graphics/cogl: unbreak with libglvnd

In file included from cogl-bitmap.c:41:
In file included from ./cogl-context-private.h:35:
In file included from ./winsys/cogl-winsys-private.h:39:
In file included from ./winsys/cogl-texture-pixmap-x11-private.h:45:
In file included from ./cogl-texture-private.h:42:
./cogl-egl-defines.h:38:10: fatal error: 'EGL/eglmesaext.h' file not found
#include <EGL/eglmesaext.h>

^~~~~~~~~~~~~~~~~~