Time-out NS event loop

Time-out NS event loop

OS X 10.10 will, at times, not send us the application-defined
event that is used to terminate the event loop.  As a workaround,
we define a timeout and react accordingly.  Leaving it in place
for other OSX and NS versions as a safety net.

Partial revert of 2014-11-08T16:32:37Z!jan.h.d@swipnet.se.

Fixes debbugs:18993