Ensures Asterisk closes when receiving terminal signals in 'no fork' mode.

When catching a signal, in no fork mode the console thread is identical to the thread
responsible for catching the signal and closing Asterisk, which requires it to first
dispense with the console thread. Prior to this patch, if these threads were identical,
upon receiving a killing signal, the thread will send an URG signal to itself, which
we also catch and then promptly do nothing with. Obviously this isn't useful behavior.

(closes issue ASTERISK-19127)
Reported By: Bryon Clark
Patches:
	quit_on_signals.patch uploaded by Bryon Clark (license 6157)
........

Merged revisions 349672 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 349673 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@349674 65c4cc65-6c06-0410-ace0-fbb531ad65f3