Even more includes

Expand the modulemap to cover some of the system headers too.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/opengl.c

@@ -9,7 +9,12 @@
  *
  */
 
+#include <string.h>
+#include <stdlib.h>
 #include <GL/glx.h>
+#include <xcb/xcb.h>
+#include <xcb/render.h>
+#include <stdio.h>
 
 #include "compiler.h"
 #include "string_utils.h"