mesa: include stdio.h where needed

Instead of relying on glapi.h or some other header to provide it.

Acked-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: José Fonseca <jfonseca@vmware.com>

src/mesa/math/m_vector.c

@@ -26,6 +26,7 @@
  * New (3.1) transformation code written by Keith Whitwell.
  */
 
+#include <stdio.h>
 
 #include "main/glheader.h"
 #include "main/imports.h"