Application::Reschedule(true) must just process all currently
pending events and ignore all new events generated while processing
them. In contrast to Scheduler::ProcessEventsToIdle, this way it
can't busy-lock the application with background jobs.

This way we also can drop nMaxEvents from the Windows backend. This
limit was also never implemented on OSX and for the KDE4 backend
it's actually impossible to handle single events, and a call to
QAbstractEventDispatcher::processEvents works like this.

Also changes various call sites to just process all pending events
instead of some made up number of times.

Change-Id: I1ab95df89b079cc8c6319a808194fe3127144d1c
Reviewed-on: https://gerrit.libreoffice.org/42659Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>