Move concat define to the one place that needs it.

include/compiler.h

 /*
  * Copyright (c) 2008-2013 Travis Geiselbrecht
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files
  * (the "Software"), to deal in the Software without restriction,
  * including without limitation the rights to use, copy, modify, merge,
  * publish, distribute, sublicense, and/or sell copies of the Software,
  * and to permit persons to whom the Software is furnished to do so,
  * subject to the following conditions:
@@ skipping 140 matching lines @@
 #define __ALWAYS_INLINE
 #define __MAY_ALIAS
 #define __NO_RETURN
 #endif
 
 #endif
 
 /* TODO: add type check */
 #define countof(a) (sizeof(a) / sizeof((a)[0]))
 
-/* macro-expanding concat */
-#define concat(a, b) __ex_concat(a, b)
-#define __ex_concat(a, b) a ## b
-
 /* CPP header guards */
 #ifdef __cplusplus
 #define __BEGIN_CDECLS  extern "C" {
 #define __END_CDECLS    }
 #else
 #define __BEGIN_CDECLS
 #define __END_CDECLS
 #endif
 
 #endif