From Lua 5.2: Add lua_copy().

Contributed by François Perrad.

src/lib_package.c

@@ -572,8 +572,7 @@ LUALIB_API int luaopen_package(lua_State *L)
   lj_lib_pushcf(L, lj_cf_package_unloadlib, 1);
   lua_setfield(L, -2, "__gc");
   luaL_register(L, LUA_LOADLIBNAME, package_lib);
-  lua_pushvalue(L, -1);
-  lua_replace(L, LUA_ENVIRONINDEX);
+  lua_copy(L, -1, LUA_ENVIRONINDEX);
   lua_createtable(L, sizeof(package_loaders)/sizeof(package_loaders[0])-1, 0);
   for (i = 0; package_loaders[i] != NULL; i++) {
     lj_lib_pushcf(L, package_loaders[i], 1);