* cygthread.cc (cygthread::stub): Very minor cleanup.

* cygthread.cc (cygthread::stub): Very minor cleanup.
(cygthread::stub): Report overflows in cygwin thread pool when DEBUGGING is on
and special environment variable is not set.
(cygthread::terminate): Set event only when event actually exists.
* exceptions.cc (signal_exit): Set priority of main thread to low before
setting current thread to high.