Win32 buildfix and warning fix.

I don't know how many pads are supposed to be supported, but I went with a reasonable number until the proper amount is committed.

Windows/DinputDevice.cpp

@@ -143,6 +143,8 @@ DinputDevice::DinputDevice(int devnum) {
 		return;
 	}
 
+	const int MAX_NUM_PADS = 4;
+
 	if (devnum >= MAX_NUM_PADS)
 	{
 		return;
@@ -318,7 +320,7 @@ void DinputDevice::ApplyButtons(DIJOYSTATE2 &state, InputState &input_state) {
 	}
 }
 
-int DinputDevice::getNumPads()
+size_t DinputDevice::getNumPads()
 {
 	if (devices.empty())
 	{

Windows/DinputDevice.h

@@ -32,7 +32,7 @@ public:
 	~DinputDevice();
 	virtual int UpdateState(InputState &input_state);
 	virtual bool IsPad() { return true; }
-	static int getNumPads();
+	static size_t getNumPads();
 private:
 	void ApplyButtons(DIJOYSTATE2 &state, InputState &input_state);
 	//unfortunate and unclean way to keep only one DirectInput instance around