introduced by the latest changes in the WMList code (multiple and empty
selection).
- added WMSetBrowserAllowMultipleSelection(), WMSetBrowserAllowEmptySelection()
WMBrowserAllowsMultipleSelection() and WMBrowserAllowsEmptySelection().
minor work and cleanup.
- made some bag and array functions to return void instead of int.
- a few new array functions.
- better handling of mouse wheel.
!!! make clean after this update before you rebuild. some enums changed.