Replace public wxEvtHandler::ProcessEventHere() with private TryHere().

Replace public wxEvtHandler::ProcessEventHere() with private TryHere().

ProcessEventHere() doesn't have to be public any more now that we have
ProcessEventLocally() which is safe to call from the outside (i.e. doesn't
forget about the chained event handlers and validators).

Still keep this function because it makes the code more modular and also
because we might want to make it virtual for consistency with TryBefore() and
TryAfter() later. Also rename it to TryHere() to make the symmetry with these
functions more manifest.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64264 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775