Reduced the number of explicit retain/release method calls on love objects. Less chance of bugs!

src/modules/thread/LuaThread.cpp

@@ -37,14 +37,11 @@ LuaThread::LuaThread(const std::string &name, love::Data *code)
 	, args(0)
 	, nargs(0)
 {
-	code->retain();
 	threadName = name;
 }
 
 LuaThread::~LuaThread()
 {
-	code->release();
-
 	// No args should still exist at this point,
 	// but you never know.
 	for (int i = 0; i < nargs; ++i)

src/modules/thread/LuaThread.h

@@ -50,7 +50,7 @@ private:
 
 	void onError();
 
-	love::Data *code;
+	Object::StrongRef<love::Data> code;
 	std::string name;
 	std::string error;