fix uninitialized use in older linux  implementation
fix uninitialized use in older linux  implementation

in the case prior to signalfd (glibc 2.8 + kernel 2.6.27),
there's no 'common signal descriptor' concept. we shouldn't
have been calling add_commonfds_to_evhandler(). prune out the
call, and check for an input signalfd < 0

dankamongmen/libtorque,dankamongmen/libtorque,dankamongmen/libtorque