dispatch: Include glheader.h in dispatch-related files.

This ensures that GLES1-only typedefs are available in these files.
In a future patch, this will allow us to expand the dispatch table to
include GLES1-only functions.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Chad Versace <chad.versace@linux.intel.com>

src/mapi/glapi/tests/check_table.cpp

@@ -22,7 +22,7 @@
  */
 
 #include <gtest/gtest.h>
-#include <GL/gl.h>
+#include "../mesa/main/glheader.h"
 
 extern "C" {
 #include "glapi/glapi.h"