Clearer distinction between types and tags

LUA_T* represents only types; tags (types + Variants) are represented
by LUA_V* constants.

lua.h

@@ -72,7 +72,7 @@ typedef struct lua_State lua_State;
 #define LUA_TUSERDATA		7
 #define LUA_TTHREAD		8
 
-#define LUA_NUMTAGS		9
+#define LUA_NUMTYPES		9
 
 
 
@@ -412,6 +412,8 @@ LUA_API void  (lua_toclose) (lua_State *L, int idx);
 #define lua_getuservalue(L,idx)	lua_getiuservalue(L,idx,1)
 #define lua_setuservalue(L,idx)	lua_setiuservalue(L,idx,1)
 
+#define LUA_NUMTAGS		LUA_NUMTYPES
+
 /* }============================================================== */
 
 /*