egl: use EGL_CAST() macro in eglmesaext.h

Allows eglmesaext.h to be used in C++ code.

This aligns this file with the rest of EGL.

Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-By: Tapani Pälli <tapani.palli@intel.com>

include/EGL/eglmesaext.h

@@ -76,7 +76,7 @@ typedef EGLBoolean (EGLAPIENTRYP PFNEGLSWAPBUFFERSREGIONNOK) (EGLDisplay dpy, EG
 
 #ifndef EGL_MESA_configless_context
 #define EGL_MESA_configless_context 1
-#define EGL_NO_CONFIG_MESA			((EGLConfig)0)
+#define EGL_NO_CONFIG_MESA			EGL_CAST(EGLConfig,0)
 #endif
 
 #ifndef EGL_MESA_drm_image_formats