'objsize' returns 'l_mem'

Sums of size_t may not fit in a size_t.

ltable.h

@@ -163,7 +163,7 @@ LUAI_FUNC Table *luaH_new (lua_State *L);
 LUAI_FUNC void luaH_resize (lua_State *L, Table *t, unsigned nasize,
                                                     unsigned nhsize);
 LUAI_FUNC void luaH_resizearray (lua_State *L, Table *t, unsigned nasize);
-LUAI_FUNC size_t luaH_size (Table *t);
+LUAI_FUNC lu_mem luaH_size (Table *t);
 LUAI_FUNC void luaH_free (lua_State *L, Table *t);
 LUAI_FUNC int luaH_next (lua_State *L, Table *t, StkId key);
 LUAI_FUNC lua_Unsigned luaH_getn (Table *t);