added memory debugging include file

lib/http.c

@@ -117,6 +117,11 @@
 #define _MPRINTF_REPLACE /* use our functions only */
 #include <curl/mprintf.h>
 
+/* The last #include file should be: */
+#ifdef MALLOCDEBUG
+#include "memdebug.h"
+#endif
+
 /*
  * This function checks the linked list of custom HTTP headers for a particular
  * header (prefix).