fix warnings (#648)

* fix unknown command line argument

* fix warnings settings for gcc

* fix -Wzero-as-null-pointer-constant

* revert CMakeLists.txt

src/logic/scripting/lua/libs/librandom.cpp

@@ -42,5 +42,5 @@ const luaL_Reg randomlib[] = {
     {"random", lua::wrap<l_random>},
     {"bytes", lua::wrap<l_bytes>},
     {"uuid", lua::wrap<l_uuid>},
-    {NULL, NULL}
+    {nullptr, nullptr}
 };