* cygthread.h (cygthread::main_thread_id): Make public.
* exceptions.cc (setup_handler): Remove unneeded priority stuff. Rename label
to reflect what it does. Add debugging for idiotic Windows NT problem. Change
debugging output to include signal number.
* miscfuncs.cc (low_priority_sleep): If available, use SwitchToThread function
to give time slice to other threads.
* wincap.cc: Properly define have_switch_to_thread throughout.
* wincap.h (wincap::switch_to_thread): New element.