build: enable -Wformat-signedness, fix issues found

Adjust code to avoid `-Wformat-signedness` warnings, while making sure
that enums are always cast to a known type when passing them to `printf`
functions, to support compilers and compiler settings where enums are
not default-size signed ints.

- cast integers printed as hex to `unsigned`. (63 times, 20 of them in
  `mbedtls.c`)
- cast misc enums to `int` for printing. (31 times)
- cast `CURL_LOCK_DATA_*` enums to `int`. (4 times)
- cast `CURL_FORMADD_*` enums to `int`. (13 times)
- cast `CURLSHE_*` enums to `int`. (3 times)
- cast `CURLUE_*` enums to `int`. (33 times)
- cast `CURLMSG_*` enums to `int`. (6 times)
- cast `CURLE_*` enums to `int`. (~380 times)
- unit1675: fix mask.
  Follow-up to 7c34365cce #21879

Ref: #18343 (initial attempt)

Closes #20848

docs/examples/10-at-a-time.c

@@ -134,14 +134,14 @@ int main(void)
           const char *url;
           CURL *curl = msg->easy_handle;
           curl_easy_getinfo(curl, CURLINFO_PRIVATE, &url);
-          fprintf(stderr, "R: %d - %s <%s>\n",
-                  msg->data.result, curl_easy_strerror(msg->data.result), url);
+          fprintf(stderr, "R: %d - %s <%s>\n", (int)msg->data.result,
+                  curl_easy_strerror(msg->data.result), url);
           curl_multi_remove_handle(multi, curl);
           curl_easy_cleanup(curl);
           left--;
         }
         else {
-          fprintf(stderr, "E: CURLMsg (%d)\n", msg->msg);
+          fprintf(stderr, "E: CURLMsg (%d)\n", (int)msg->msg);
         }
         if(transfers < NUM_URLS)
           add_transfer(multi, transfers++, &left);

docs/examples/externalsocket.c

@@ -164,7 +164,7 @@ int main(void)
     close(sockfd);
 
     if(result != CURLE_OK) {
-      printf("libcurl error: %d\n", result);
+      printf("libcurl error: %d\n", (int)result);
       return 4;
     }
   }

docs/examples/ftp-delete.c

@@ -74,7 +74,7 @@ int main(void)
 
     if(result != CURLE_OK) {
       /* we failed */
-      fprintf(stderr, "curl told us %d\n", result);
+      fprintf(stderr, "curl told us %d\n", (int)result);
     }
   }
 

docs/examples/ftpget.c

@@ -87,7 +87,7 @@ int main(void)
 
     if(result != CURLE_OK) {
       /* we failed */
-      fprintf(stderr, "curl told us %d\n", result);
+      fprintf(stderr, "curl told us %d\n", (int)result);
     }
   }
 

docs/examples/ftpgetinfo.c

@@ -90,7 +90,7 @@ int main(void)
     }
     else {
       /* we failed */
-      fprintf(stderr, "curl told us %d\n", result);
+      fprintf(stderr, "curl told us %d\n", (int)result);
     }
 
     /* always cleanup */

docs/examples/ftpsget.c

@@ -92,7 +92,7 @@ int main(void)
 
     if(result != CURLE_OK) {
       /* we failed */
-      fprintf(stderr, "curl told us %d\n", result);
+      fprintf(stderr, "curl told us %d\n", (int)result);
     }
   }
 

docs/examples/log_failed_transfers.c

@@ -289,7 +289,7 @@ int main(void)
         failed = 0;
       }
       else {
-        mem_addf(&t->log, "Transfer failed: (%d) %s\n", result,
+        mem_addf(&t->log, "Transfer failed: (%d) %s\n", (int)result,
                  (errbuf[0] ? errbuf : curl_easy_strerror(result)));
         fprintf(stderr, "%s", t->log.recent);
         failed = 1;

docs/examples/multi-app.c

@@ -99,10 +99,12 @@ int main(void)
 
         switch(idx) {
         case HTTP_HANDLE:
-          printf("HTTP transfer completed with status %d\n", msg->data.result);
+          printf("HTTP transfer completed with status %d\n",
+                 (int)msg->data.result);
           break;
         case FTP_HANDLE:
-          printf("FTP transfer completed with status %d\n", msg->data.result);
+          printf("FTP transfer completed with status %d\n",
+                 (int)msg->data.result);
           break;
         }
       }

docs/examples/multi-legacy.c

@@ -177,10 +177,12 @@ int main(void)
 
         switch(idx) {
         case HTTP_HANDLE:
-          printf("HTTP transfer completed with status %d\n", msg->data.result);
+          printf("HTTP transfer completed with status %d\n",
+                 (int)msg->data.result);
           break;
         case FTP_HANDLE:
-          printf("FTP transfer completed with status %d\n", msg->data.result);
+          printf("FTP transfer completed with status %d\n",
+                 (int)msg->data.result);
           break;
         }
       }

docs/examples/sftpget.c

@@ -103,7 +103,7 @@ int main(void)
 
     if(result != CURLE_OK) {
       /* we failed */
-      fprintf(stderr, "curl told us %d\n", result);
+      fprintf(stderr, "curl told us %d\n", (int)result);
     }
   }
 

docs/examples/sslbackend.c

@@ -54,7 +54,7 @@ int main(int argc, const char **argv)
 
     for(i = 0; list[i]; i++)
       printf("SSL backend #%d: '%s' (ID: %d)\n",
-             i, list[i]->name, list[i]->id);
+             i, list[i]->name, (int)list[i]->id);
 
     return 0;
   }

docs/examples/websocket-updown.c

@@ -69,7 +69,7 @@ static size_t read_cb(char *buf, size_t nitems, size_t buflen, void *p)
     result = curl_ws_start_frame(ctx->curl, CURLWS_TEXT,
                                  (curl_off_t)ctx->blen);
     if(result != CURLE_OK) {
-      fprintf(stderr, "error starting frame: %d\n", result);
+      fprintf(stderr, "error starting frame: %d\n", (int)result);
       return CURL_READFUNC_ABORT;
     }
   }

docs/examples/websocket.c

@@ -94,7 +94,7 @@ retry:
     else {
       /* some other frame arrived. */
       fprintf(stderr, "ws: received frame of %u bytes rflags %x\n",
-              (unsigned int)rlen, meta->flags);
+              (unsigned int)rlen, (unsigned int)meta->flags);
       goto retry;
     }
   }