fix explanation output by configure script to refer to Aquamacs.app
Workaround for hang on 10.10: use timeout in NS event loop
The NS event loop normally terminates by receiving an AppDefined event
that it sends to itself.  This mechanism fails on 10.10 after
rapid clicks on the toolbar (the AppDefined event is sent, but
never received).  Therefore, a short (0.5sec) timeout is enforced.