Instead of storing the system ticks in the timer event message
simply store a version.

Moves the version handling code into a VersionedEvent class,
inherited by WinSalTimer and AquaSalTimer.

Change-Id: I5add85031d36b3424a26a9ef798294cbfb00b2e4
Reviewed-on: https://gerrit.libreoffice.org/42959Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>