- I did a cleanup of the internal generic SSL layer and how the various SSL

libraries are supported. Starting now, each underlying SSL library support
  code does a set of defines for the 16 functions the generic layer (sslgen.c)
  uses (all these new function defines use the prefix "curlssl_"). This
  greatly simplified the generic layer in readability by involving much less
  #ifdefs and other preprocessor stuff and should make it easier for people to
  make libcurl work with new SSL libraries.

  Hopefully I can later on document these 16 functions somewhat as well.

  I also made most of the internal SSL-dependent functions (using Curl_ssl_
  prefix) #defined to nothing when no SSL support is requested - previously
  they would unnecessarily call mostly empty functions.

lib/gtls.h

@@ -22,6 +22,9 @@
  *
  * $Id$
  ***************************************************************************/
+
+#ifdef USE_GNUTLS
+
 int Curl_gtls_init(void);
 int Curl_gtls_cleanup(void);
 CURLcode Curl_gtls_connect(struct connectdata *conn, int sockindex);
@@ -45,4 +48,22 @@ void Curl_gtls_session_free(void *ptr);
 size_t Curl_gtls_version(char *buffer, size_t size);
 int Curl_gtls_shutdown(struct connectdata *conn, int sockindex);
 
+/* API setup for GnuTLS */
+#define curlssl_init Curl_gtls_init
+#define curlssl_cleanup Curl_gtls_cleanup
+#define curlssl_connect Curl_gtls_connect
+#define curlssl_session_free(x)  Curl_gtls_session_free(x)
+#define curlssl_close_all Curl_gtls_close_all
+#define curlssl_close Curl_gtls_close
+#define curlssl_shutdown(x,y) Curl_gtls_shutdown(x,y)
+#define curlssl_set_engine(x,y) (x=x, y=y, CURLE_FAILED_INIT)
+#define curlssl_set_engine_default(x) (x=x, CURLE_FAILED_INIT)
+#define curlssl_engines_list(x) (x=x, NULL)
+#define curlssl_send Curl_gtls_send
+#define curlssl_recv Curl_gtls_recv
+#define curlssl_version Curl_gtls_version
+#define curlssl_check_cxn(x) (x=x, -1)
+#define curlssl_data_pending(x,y) (x=x, y=y, 0)
+
+#endif /* USE_GNUTLS */
 #endif