* fhandler.cc (fhandler_disk_file::fstat): Don't rely on exactly 3 characters

* fhandler.cc (fhandler_disk_file::fstat): Don't rely on exactly 3 characters
being read for executable test since we could be checking for less than that.
* syscalls.cc (stat_worker): Try opening the file the "correct" way first so
that #! processing can potentially happen.  If that fails, then use "query
open" method.
* spawn.cc (spawn_guts): Delay processing of signal until after we've notified
parent about reparenting.