* gdb.base/corefile.exp: Change xfail for backtrace in

	* gdb.base/corefile.exp:  Change xfail for backtrace in
	corefile.exp from linuxaout to all linux.
	* gdb.base/sigall.exp (test_one_sig):  Specifically deal with
	cases where we miss the breakpoint at the signal handler
	for some reason.  Setup xfail for linuxoldld/linuxaout and
	getting SIGIO.  Setup xfail for linuxoldld/linuxaout for
	hitting SIGURG breakpoint.
	* gdb.base/signals.exp:  Setup xfail for "next" acting like
	continue to add linuxoldld.  Setup xfail for all linux for
	"next to handler in signals_tests_1", "backtrace in
	signals_tests_1", "continue to func1", "pass SIGUSR1",
	and continue to handler".