- Removed USE_GETTICKCOUNT code; it's never used now.
- Reduced the number of preprocessor checks for WinRT.
- Renamed timeSetPeriod() so it doesn't look like a Win32 API call.
An existing hint lets apps that don't need the timer resolution changed avoid
this, to save battery, etc, but this fixes several problems in timing, audio
callbacks not firing fast enough, etc.
Fixes Bugzilla #2944.