weston-egl-ext.h: add EGL_MESA_configless_context definitions

... and use it in gl-renderer.

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
diff --git a/libweston/weston-egl-ext.h b/libweston/weston-egl-ext.h
index f5420ba..6bb401d 100644
--- a/libweston/weston-egl-ext.h
+++ b/libweston/weston-egl-ext.h
@@ -121,5 +121,10 @@
 typedef EGLBoolean (EGLAPIENTRYP PFNEGLSWAPBUFFERSWITHDAMAGEEXTPROC) (EGLDisplay dpy, EGLSurface surface, EGLint *rects, EGLint n_rects);
 #endif /* EGL_EXT_swap_buffers_with_damage */
 
+#ifndef EGL_MESA_configless_context
+#define EGL_MESA_configless_context 1
+#define EGL_NO_CONFIG_MESA                      ((EGLConfig)0)
+#endif
+
 
 #endif