* DevNotes: Add entry cgf-000022.
* cygtls.h (_cygtls::func): Define as a sa_sigaction style function.
* exceptions.cc (sig_handle_tty_stop): Ditto.
(_cygtls::interrupt_setup): Fix coercion to accommodate 'func' change.
(ctrl_c_handler): Use tty kill_pgrp to send a signal.
(sigpacket::process): Don't process sigflush here.
(_cygtls::call_signal_handler): Reorganize to avoid a race.  Always call
sa_sigaction style function.
* fhandler_termios.cc (is_flush_sig): Define new function.
(tty_min::kill_pgrp): Handle tty flush when signal detected.
(fhandler_termios::bg_check): Be slightly more paranoid about checking for
valid tty.
(fhandler_termios::sigflush): Don't flush unless tty owner.
* fhandler_tty.cc (fhandler_pty_slave::ioctl): Use tty kill_pgrp to send
signal.
(fhandler_pty_master::ioctl): Ditto.
* signal.cc (killsys): Delete definition.
* sigproc.h (killsys): Delete declaration.
* include/cygwin/signal.h (siginfo_t): Simplify union/struct nesting slightly.
Implement mechanism to allow cygwin data passing.