configure, cmake, lib: more form api deprecation

Introduce a --enable-form-api configure option to control its inclusion
in builds. The condition name defined for it is CURL_DISABLE_FORM_API.

Form api code is dependent of MIME: configure and CMake handle this
dependency automatically: CMake by making it a dependent option
explicitly, configure by inheriting the MIME value by default and
rejecting explicit incompatible values.

"form-api" is now a new hidden test feature.

Update libcurl modules to respect this option and adjust tests
accordingly.

Closes #9621

lib/curl_config.h.cmake

@@ -50,6 +50,9 @@
 /* disables FILE */
 #cmakedefine CURL_DISABLE_FILE 1
 
+/* disables form api */
+#cmakedefine CURL_DISABLE_FORM_API 1
+
 /* disables FTP */
 #cmakedefine CURL_DISABLE_FTP 1
 

lib/formdata.c

@@ -27,7 +27,7 @@
 #include <curl/curl.h>
 
 #include "formdata.h"
-#if !defined(CURL_DISABLE_HTTP) && !defined(CURL_DISABLE_MIME)
+#if !defined(CURL_DISABLE_HTTP) && !defined(CURL_DISABLE_FORM_API)
 
 #if defined(HAVE_LIBGEN_H) && defined(HAVE_BASENAME)
 #include <libgen.h>
@@ -941,7 +941,7 @@ int curl_formget(struct curl_httppost *form, void *arg,
 void curl_formfree(struct curl_httppost *form)
 {
   (void)form;
-  /* does nothing HTTP is disabled */
+  /* Nothing to do. */
 }
 
 #endif  /* if disabled */

lib/formdata.h

@@ -26,7 +26,7 @@
 
 #include "curl_setup.h"
 
-#ifndef CURL_DISABLE_MIME
+#ifndef CURL_DISABLE_FORM_API
 
 /* used by FormAdd for temporary storage */
 struct FormInfo {
@@ -53,10 +53,7 @@ CURLcode Curl_getformdata(struct Curl_easy *data,
                           curl_mimepart *,
                           struct curl_httppost *post,
                           curl_read_callback fread_func);
-#else
-/* disabled */
-#define Curl_getformdata(a,b,c,d) CURLE_NOT_BUILT_IN
-#endif
+#endif /* CURL_DISABLE_FORM_API */
 
 
 #endif /* HEADER_CURL_FORMDATA_H */

lib/http.c

@@ -2372,6 +2372,7 @@ CURLcode Curl_http_body(struct Curl_easy *data, struct connectdata *conn,
   case HTTPREQ_POST_MIME:
     http->sendit = &data->set.mimepost;
     break;
+#ifndef CURL_DISABLE_FORM_API
   case HTTPREQ_POST_FORM:
     /* Convert the form structure into a mime structure. */
     Curl_mime_cleanpart(&http->form);
@@ -2381,6 +2382,7 @@ CURLcode Curl_http_body(struct Curl_easy *data, struct connectdata *conn,
       return result;
     http->sendit = &http->form;
     break;
+#endif
   default:
     http->sendit = NULL;
   }

lib/setopt.c

@@ -666,7 +666,7 @@ CURLcode Curl_vsetopt(struct Curl_easy *data, CURLoption option, va_list param)
       data->set.method = HTTPREQ_GET;
     break;
 
-#ifndef CURL_DISABLE_MIME
+#ifndef CURL_DISABLE_FORM_API
   case CURLOPT_HTTPPOST:
     /*
      * Set to make us do HTTP POST