fix compiler warning: external declaration in primary source file

lib/mprintf.c

@@ -180,8 +180,6 @@ struct asprintf {
                    the output is not the complete data */
 };
 
-int curl_msprintf(char *buffer, const char *format, ...);
-
 static long dprintf_DollarString(char *input, char **end)
 {
   int number=0;

packages/OS400/ccsidcurl.c

@@ -33,6 +33,7 @@
 #pragma enum(int)
 
 #include <curl/curl.h>
+#include <curl/mprintf.h>
 #include "urldata.h"
 #include "url.h"
 #include "getinfo.h"