* select.cc (allocfd_set): Try to make a little more efficient.
(cygwin_select): Break into two functions to avoid what seems to be a strange
compiler problem with alloca and sel constructor.
(select): New function. Always honor return from call_signal_handler.
(select_stuff::wait): Always honor return from call_signal_handler.
* select.h (select_stuff::select_stuff): Use NULL to initialize pointers rather
than 0.
(cancelable_wait): Define variant which accepts DWORD time argument.
(cygwait): Use cancelable_wait with DWORD argument.
(cygwait): Use cancelable_wait with DWORD argument and cw_sig_eintr for
timeout-only case.
* exceptions.cc (handle_sigsuspend): Use LARGE_NULL as second argument to
distinguish between cancelable_wait variants.
* thread.cc (pthread_mutex::lock): Ditto.
(pthread::join): Ditto.
(semaphore::_timedwait): Ditto.
* thread.h (fast_mutex::lock): Ditto.
* wait.cc (wait4): Ditto.
