Windows/Audio: add listener for device change

For some reason XAudio2 doesn't automatically change the device anymore.
So let's just listen for the OnDefaultDeviceChanged event and update the cell audio thread if necessary.

Utilities/StrFmt.cpp

@@ -16,7 +16,7 @@
 #endif
 
 #ifdef _WIN32
-std::string wchar_to_utf8(wchar_t *src)
+std::string wchar_to_utf8(const wchar_t *src)
 {
 	std::string utf8_string;
 	const auto tmp_size = WideCharToMultiByte(CP_UTF8, 0, src, -1, nullptr, 0, nullptr, nullptr);