introduce c11_compat.h to provide C11 things in C99

Right now, all it does is provide the new standard `static_assert()` name.

Fixes: fbf7c38da3 ("egl/wayland: use bitset.h for `formats` bit set")
Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Tested-by: Bhushan Shah <bshah@kde.org>

src/util/macros.h

@@ -27,6 +27,7 @@
 #include <assert.h>
 
 #include "c99_compat.h"
+#include "c11_compat.h"
 
 /* Compute the size of an array */
 #ifndef ARRAY_SIZE