Make Unix wxAppConsole signal handling more flexible.

Make Unix wxAppConsole signal handling more flexible.

Instead of hardcoding the call to WakeUpIdle() in the signal handler itself,
just wake up the event loop when we catch a signal. This will still result in
WakeUpIdle() being called, before the next event loop iteration, but it will
also allow us to do other things on wakeup from signal as it will be done in
the upcoming wxExecute() changes to support wxEXEC_NOEVENTS in console
applications.

See #10258.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74347 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775