curl.h: define CURL_DID_MEMORY_FUNC_TYPEDEFS

So that we only do the extra typedefs in curl_memory.h when we really
need to and avoid double typedefs.

follow-up commit to 7218b52c49

Thanks-to: Steve Holme

include/curl/curl.h

@@ -7,7 +7,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2015, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -385,6 +385,8 @@ typedef void *(*curl_realloc_callback)(void *ptr, size_t size);
 typedef char *(*curl_strdup_callback)(const char *str);
 typedef void *(*curl_calloc_callback)(size_t nmemb, size_t size);
 
+#define CURL_DID_MEMORY_FUNC_TYPEDEFS
+
 /* the kind of data that is passed to information_callback*/
 typedef enum {
   CURLINFO_TEXT = 0,

lib/curl_memory.h

@@ -83,6 +83,7 @@
 
 #ifndef CURLX_NO_MEMORY_CALLBACKS
 
+#ifndef CURL_DID_MEMORY_FUNC_TYPEDEFS /* only if not already done */
 /*
  * The following memory funciton replacement typedef's are COPIED from
  * curl/curl.h and MUST match the originals. We copy them to avoid having to
@@ -94,7 +95,7 @@ typedef void (*curl_free_callback)(void *ptr);
 typedef void *(*curl_realloc_callback)(void *ptr, size_t size);
 typedef char *(*curl_strdup_callback)(const char *str);
 typedef void *(*curl_calloc_callback)(size_t nmemb, size_t size);
-
+#endif
 
 extern curl_malloc_callback Curl_cmalloc;
 extern curl_free_callback Curl_cfree;