Abolishing sleeps in issignal()

[Mike Karels]

> What I'd like from readers on arch@ is for you to consider if there are 
> other cases than non-restartable syscalls that will break if 
> msleep/sleepqs return EINTR from SIGSTOP and debug events.  Also, is there 
> an authoritative list of non-restartable syscalls anywhere?  It's just 
> those involving timevals right?  nanosleep/poll/select/kqueue.. others?

Don't forget about siginterrupt, which can make specified syscalls
interrupt read/read etc.

		Mike