Fix compilation errors with the UWP build.

miniaudio.h

@@ -17397,11 +17397,13 @@ typedef int     (WINAPI * MA_PFN_StringFromGUID2)(const GUID* const rguid, LPOLE
 typedef HWND (WINAPI * MA_PFN_GetForegroundWindow)(void);
 typedef HWND (WINAPI * MA_PFN_GetDesktopWindow)(void);
 
+#if defined(MA_WIN32_DESKTOP)
 /* Microsoft documents these APIs as returning LSTATUS, but the Win32 API shipping with some compilers do not define it. It's just a LONG. */
 typedef LONG (WINAPI * MA_PFN_RegOpenKeyExA)(HKEY hKey, LPCSTR lpSubKey, DWORD ulOptions, REGSAM samDesired, PHKEY phkResult);
 typedef LONG (WINAPI * MA_PFN_RegCloseKey)(HKEY hKey);
 typedef LONG (WINAPI * MA_PFN_RegQueryValueExA)(HKEY hKey, LPCSTR lpValueName, LPDWORD lpReserved, LPDWORD lpType, LPBYTE lpData, LPDWORD lpcbData);
-#endif
+#endif  /* MA_WIN32_DESKTOP */
+#endif  /* MA_WIN32 */
 
 
 #define MA_DEFAULT_PLAYBACK_DEVICE_NAME    "Default Playback Device"