* exceptions.cc (handle_sigsuspend): Force pending signal delivery before

* exceptions.cc (handle_sigsuspend): Force pending signal delivery before
waiting for signals to happen.
* signal.cc (sleep): Force pending signal delivery before sleeping.
(usleep): Ditto.
(signal): Force pending signal delivery before manipulating signal stuff.
(sigprocmask): Ditto.
(kill_worker): Ditto.
(abort): Ditto.
(sigaction): Ditto.
* syscalls.cc (readv): Force pending signal delivery before I/O.
(writev): Ditto.
(open): Ditto.
* net.cc: Ditto, throughout.
* sigproc.cc (sig_dispatch_pending): Deliver any pending signals prior to
returning.
* tty.cc (tty::make_pipes): Increase pipe buffer size.