llimits.h being used by all Lua code

The definitions in llimits.h are useful not only for the core. That
header only defines types and '#define's, so libs and core still do
not share any real code/data.

lua.c

@@ -19,6 +19,7 @@
 
 #include "lauxlib.h"
 #include "lualib.h"
+#include "llimits.h"
 
 
 #if !defined(LUA_PROGNAME)