* gdb.base/a1-selftest.exp: Change x86 linux setup_xfails to

	* gdb.base/a1-selftest.exp: Change x86 linux setup_xfails to
	use new i*86-pc-linux*-gnu quads.
	* gdb.base/corefile.exp: Ditto.
	* gdb.base/signals.exp: Ditto.
	* gdb.base/sigall.exp: Ditto.
	* gdb.base/interrupt.exp: Ditto.

	* gdb.base/signals.exp (signal_tests_1): Remove setup_xfail
	"i*86-*-linux" for "signal SIGUSR1".  Now works, at least with
	RedHat 4.0.

	* gdb.threads/pthreads.c (_MIT_POSIX_THREADS): Define if target is
 	linux.  This allows the test case to at least compile on latest
 	linux, but still not run due to missing the threads runtime library.