Warning fixes:

- Don't use %lu for size_t; they're different on Linux x86.

- has_warned_about_drivers is only used on win32, so only declare it
  there to avoid a unused variable warning.

Source/Core/Core/Src/IPC_HLE/WII_IPC_HLE_Device_hid.cpp

@@ -523,7 +523,9 @@ libusb_device_handle * CWII_IPC_HLE_Device_hid::GetDeviceByDevNum(u32 devNum)
 	if (cnt < 0)
 		return NULL;
 	
+#ifdef _WIN32
 	static bool has_warned_about_drivers = false;
+#endif
 
 	for (i = 0; i < cnt; i++) {
 		libusb_device *device = list[i];