Update changelog in OS X windowed copy

Add entries for 1.11.8 and 1.11.9.  This should have been done for the
previous two releases, but I did not know about this.  It will be done
correctly for 1.11.10.

Thanks to Alarantalara for the pointers.
Update link to changelog in OS X windowed copy to github

Was still set to svn.gna.org