- more fixes for GCC

error: ‘size_t’ does not name a type
error: ‘assert’ was not declared in this scope

src/hwrenderer/data/buffers.h

@@ -1,5 +1,8 @@
 #pragma once
 
+#include <stddef.h>
+#include <assert.h>
+
 // The low level code needs to know which attributes exist.
 // OpenGL needs to change the state of all of them per buffer binding.
 // VAOs are mostly useless for this because they lump buffer and binding state together which the model code does not want.