Update announcement and readme files for 2.9.5 release.

Fill in the release date and update the changes description in the
announcement.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74413 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Exclude expat files from pre commit hook checks too.

All the other 3rd party libraries were already excluded but not this one, for
some reason -- do exclude it now as upcoming Expat 2.1.0 sources contain some
files with TABs.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74414 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775