build: stop overriding standard memory allocation functions

Before this patch curl used the C preprocessor to override standard
memory allocation symbols: malloc, calloc, strdup, realloc, free.
The goal of these is to replace them with curl's debug wrappers in
`CURLDEBUG` builds, another was to replace them with the wrappers
calling user-defined allocators in libcurl. This solution needed a bunch
of workarounds to avoid breaking external headers: it relied on include
order to do the overriding last. For "unity" builds it needed to reset
overrides before external includes. Also in test apps, which are always
built as single source files. It also needed the `(symbol)` trick
to avoid overrides in some places. This would still not fix cases where
the standard symbols were macros. It was also fragile and difficult
to figure out which was the actual function behind an alloc or free call
in a specific piece of code. This in turn caused bugs where the wrong
allocator was accidentally called.

To avoid these problems, this patch replaces this solution with
`curlx_`-prefixed allocator macros, and mapping them _once_ to either
the libcurl wrappers, the debug wrappers or the standard ones, matching
the rest of the code in libtests.

This concludes the long journey to avoid redefining standard functions
in the curl codebase.

Note: I did not update `packages/OS400/*.c` sources. They did not
`#include` `curl_setup.h`, `curl_memory.h` or `memdebug.h`, meaning
the overrides were never applied to them. This may or may not have been
correct. For now I suppressed the direct use of standard allocators
via a local `.checksrc`. Probably they (except for `curlcl.c`) should be
updated to include `curl_setup.h` and use the `curlx_` macros.

This patch changes mappings in two places:
- `lib/curl_threads.c` in libtests: Before this patch it mapped to
  libcurl allocators. After, it maps to standard allocators, like
  the rest of libtests code.
- `units`: before this patch it mapped to standard allocators. After, it
  maps to libcurl allocators.

Also:
- drop all position-dependent `curl_memory.h` and `memdebug.h` includes,
  and delete the now unnecessary headers.
- rename `Curl_tcsdup` macro to `curlx_tcsdup` and define like the other
  allocators.
- map `curlx_strdup()` to `_strdup()` on Windows (was: `strdup()`).
  To fix warnings silenced via `_CRT_NONSTDC_NO_DEPRECATE`.
- multibyte: map `curlx_convert_*()` to `_strdup()` on Windows
  (was: `strdup()`).
- src: do not reuse the `strdup` name for the local replacement.
- lib509: call `_strdup()` on Windows (was: `strdup()`).
- test1132: delete test obsoleted by this patch.
- CHECKSRC.md: update text for `SNPRINTF`.
- checksrc: ban standard allocator symbols.

Follow-up to b12da22db1 #18866
Follow-up to db98daab05 #18844
Follow-up to 4deea9396b #18814
Follow-up to 9678ff5b1b #18776
Follow-up to 10bac43b87 #18774
Follow-up to 20142f5d06 #18634
Follow-up to bf7375ecc5 #18503
Follow-up to 9863599d69 #18502
Follow-up to 3bb5e58c10 #17827

Closes #19626

lib/cookie.c

@@ -42,10 +42,6 @@
 #include "llist.h"
 #include "curlx/strparse.h"
 
-/* The last 2 #include files should be in this order */
-#include "curl_memory.h"
-#include "memdebug.h"
-
 static void strstore(char **str, const char *newstr, size_t len);
 
 /* number of seconds in 400 days */
@@ -70,12 +66,12 @@ static void cap_expires(time_t now, struct Cookie *co)
 
 static void freecookie(struct Cookie *co)
 {
-  free(co->domain);
-  free(co->path);
-  free(co->spath);
-  free(co->name);
-  free(co->value);
-  free(co);
+  curlx_free(co->domain);
+  curlx_free(co->path);
+  curlx_free(co->spath);
+  curlx_free(co->name);
+  curlx_free(co->value);
+  curlx_free(co);
 }
 
 static bool cookie_tailmatch(const char *cookie_domain,
@@ -246,7 +242,7 @@ static char *sanitize_cookie_path(const char *cookie_path)
   /* RFC6265 5.2.4 The Path Attribute */
   if(cookie_path[0] != '/')
     /* Let cookie-path be the default-path. */
-    return strdup("/");
+    return curlx_strdup("/");
 
   /* remove trailing slash when path is non-empty */
   /* convert /hoge/ to /hoge */
@@ -268,7 +264,7 @@ static char *sanitize_cookie_path(const char *cookie_path)
 static void strstore(char **str, const char *newstr, size_t len)
 {
   DEBUGASSERT(str);
-  free(*str);
+  curlx_free(*str);
   if(!len) {
     len++;
     newstr = "";
@@ -506,7 +502,7 @@ parse_cookie_header(struct Curl_easy *data,
         strstore(&co->path, curlx_str(&val), curlx_strlen(&val));
         if(!co->path)
           return CURLE_OUT_OF_MEMORY;
-        free(co->spath); /* if this is set again */
+        curlx_free(co->spath); /* if this is set again */
         co->spath = sanitize_cookie_path(co->path);
         if(!co->spath)
           return CURLE_OUT_OF_MEMORY;
@@ -631,7 +627,7 @@ parse_cookie_header(struct Curl_easy *data,
 
   if(!co->domain && domain) {
     /* no domain was given in the header line, set the default */
-    co->domain = strdup(domain);
+    co->domain = curlx_strdup(domain);
     if(!co->domain)
       return CURLE_OUT_OF_MEMORY;
   }
@@ -739,10 +735,10 @@ parse_netscape(struct Cookie *co,
         break;
       }
       /* this does not look like a path, make one up! */
-      co->path = strdup("/");
+      co->path = curlx_strdup("/");
       if(!co->path)
         return CURLE_OUT_OF_MEMORY;
-      co->spath = strdup("/");
+      co->spath = curlx_strdup("/");
       if(!co->spath)
         return CURLE_OUT_OF_MEMORY;
       fields++; /* add a field and fall down to secure */
@@ -781,7 +777,7 @@ parse_netscape(struct Cookie *co,
   }
   if(fields == 6) {
     /* we got a cookie with blank contents, fix it */
-    co->value = strdup("");
+    co->value = curlx_strdup("");
     if(!co->value)
       return CURLE_OUT_OF_MEMORY;
     else
@@ -981,7 +977,7 @@ Curl_cookie_add(struct Curl_easy *data,
     return CURLE_OK; /* silently ignore */
 
   /* First, alloc and init a new struct for it */
-  co = calloc(1, sizeof(struct Cookie));
+  co = curlx_calloc(1, sizeof(struct Cookie));
   if(!co)
     return CURLE_OUT_OF_MEMORY; /* bail out if we are this low on memory */
 
@@ -1081,7 +1077,7 @@ fail:
 struct CookieInfo *Curl_cookie_init(void)
 {
   int i;
-  struct CookieInfo *ci = calloc(1, sizeof(struct CookieInfo));
+  struct CookieInfo *ci = curlx_calloc(1, sizeof(struct CookieInfo));
   if(!ci)
     return NULL;
 
@@ -1343,7 +1339,7 @@ CURLcode Curl_cookie_getlist(struct Curl_easy *data,
     size_t i;
 
     /* alloc an array and store all cookie pointers */
-    array = malloc(sizeof(struct Cookie *) * matches);
+    array = curlx_malloc(sizeof(struct Cookie *) * matches);
     if(!array) {
       result = CURLE_OUT_OF_MEMORY;
       goto fail;
@@ -1363,7 +1359,7 @@ CURLcode Curl_cookie_getlist(struct Curl_easy *data,
     for(i = 0; i < matches; i++)
       Curl_llist_append(list, array[i], &array[i]->getnode);
 
-    free(array); /* remove the temporary data again */
+    curlx_free(array); /* remove the temporary data again */
   }
 
   *okay = TRUE;
@@ -1435,7 +1431,7 @@ void Curl_cookie_cleanup(struct CookieInfo *ci)
 {
   if(ci) {
     Curl_cookie_clearall(ci);
-    free(ci); /* free the base struct as well */
+    curlx_free(ci); /* free the base struct as well */
   }
 }
 
@@ -1518,7 +1514,7 @@ static CURLcode cookie_output(struct Curl_easy *data,
     struct Cookie **array;
     struct Curl_llist_node *n;
 
-    array = calloc(1, sizeof(struct Cookie *) * ci->numcookies);
+    array = curlx_calloc(1, sizeof(struct Cookie *) * ci->numcookies);
     if(!array) {
       error = CURLE_OUT_OF_MEMORY;
       goto error;
@@ -1540,15 +1536,15 @@ static CURLcode cookie_output(struct Curl_easy *data,
     for(i = 0; i < nvalid; i++) {
       char *format_ptr = get_netscape_format(array[i]);
       if(!format_ptr) {
-        free(array);
+        curlx_free(array);
         error = CURLE_OUT_OF_MEMORY;
         goto error;
       }
       curl_mfprintf(out, "%s\n", format_ptr);
-      free(format_ptr);
+      curlx_free(format_ptr);
     }
 
-    free(array);
+    curlx_free(array);
   }
 
   if(!use_stdout) {
@@ -1565,7 +1561,7 @@ static CURLcode cookie_output(struct Curl_easy *data,
    * no need to inspect the error, any error case should have jumped into the
    * error block below.
    */
-  free(tempstore);
+  curlx_free(tempstore);
   return CURLE_OK;
 
 error:
@@ -1573,7 +1569,7 @@ error:
     curlx_fclose(out);
   if(tempstore) {
     unlink(tempstore);
-    free(tempstore);
+    curlx_free(tempstore);
   }
   return error;
 }
@@ -1605,7 +1601,7 @@ static struct curl_slist *cookie_list(struct Curl_easy *data)
       }
       beg = Curl_slist_append_nodup(list, line);
       if(!beg) {
-        free(line);
+        curlx_free(line);
         curl_slist_free_all(list);
         return NULL;
       }