Fix iterating over pending signals if a signal doesn't have to be cleared

Fix iterating over pending signals if a signal doesn't have to be cleared

	* sigproc.cc (pending_signals::clear): Yet another fix to fix the fix.
	Actually iterate over the list of pending signals even if there's a
	signal which doesn't have to be cleared.  Other than that, revert loop
	to it's former self as a while loop.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>