Add some more extensions from Lua 5.2/5.3.

Contributed by François Perrad.

src/lib_package.c

@@ -589,6 +589,10 @@ LUALIB_API int luaopen_package(lua_State *L)
     lj_lib_pushcf(L, package_loaders[i], 1);
     lua_rawseti(L, -2, i+1);
   }
+#if LJ_52
+  lua_pushvalue(L, -1);
+  lua_setfield(L, -3, "searchers");
+#endif
   lua_setfield(L, -2, "loaders");
   lua_getfield(L, LUA_REGISTRYINDEX, "LUA_NOENV");
   noenv = lua_toboolean(L, -1);