* exceptions.cc (setup_handler): Improve debugging output.
(call_signal_handler_now): Remove ill-advised debugger call.
* sigproc.cc (sigcomplete_main): Delete.
(sig_send): Honor FIXME and avoid using main thread's completion event for
everything or suffer races.
(pending_signals::add): Default stored mask to current process mask rather than
mask at time of signal send.
(wait_sig): Add debugging output.
* sigproc.h (sigpacket::mask_storage): Delete.