Add TApplication::HandleException() method, which gets called by
TSystem::DispatchSignals() in case of an exception (sigbus, sigsegv, sigill
or sigfpe). In derived TApplication's one might now want to not throw
or do something else to reset the environment.


git-svn-id: http://root.cern.ch/svn/root/trunk@20680 27541ba8-7e3a-0410-8455-c3a389f83636