conformtest: Support xfail markers on individual assertions.

conformtest: Support xfail markers on individual assertions.

Various conformtest tests fail because of known issues, filed in
Bugzilla, that are hard to fix (requiring new features, kernel
cooperation or involving changing types in ways that may involve care
around padding when interfacing to the kernel).  Such an issue has the
effect of making the whole test for the (standard, header) pair fail,
so hiding any other issues with that header for that standard
(possibly regressions or architecture-specific issues).

This patch adds a mechanism for individual conformtest test
expectations to start with xfail-, meaning that a failure of that
particular assertion does not cause the whole test to fail at the
makefile level and so failure at the makefile level can be used to
detect other issues that are likely to be easier to fix.  This is
similar to the whitelisted symbols in the linknamespace tests, or the
marking of particular libm tests as allowing spurious or missing
exceptions, for example.  The bugs filed in Bugzilla should still be
fixed, and the xfail- markers removed at that point, but xfail-
renders the tests more useful until that happens.

Note that there is no way to add such a marker for the assertion that
a header uses only symbols in the namespace of symbols it's meant to
use.  I don't think there's any need for a way to xfail those
namespace tests other than xfailing the whole (standard, header) pair
at the makefile level, since they are generally straightforward to fix
(add appropriate conditionals on the problem definitions).

The xfails in this patch do not necessarily cover all cases of
hard-to-fix header bugs filed in Bugzilla that currently show up in
conformtest failures; there may be more yet to add for existing open
bugs.

Tested for x86_64 and x86.

	* conform/conformtest.pl ($xerrors): New variable.
	(note_error): New function.
	(compiletest): New argument $xfail.  Use not_error.
	(runtest): Likewise.
	(top level): Handle xfail- lines.  Update calls to compiletest and
	runtest.  Handle xfail- and optional- in headers listed with
	allow-header.
	* conform/data/fcntl.h-data (O_TTY_INIT): Use xfail-.
	(O_EXEC): Likewise.
	(O_SEARCH): Likewise.
	* conform/data/stropts.h-data (ioctl): Likewise.
	* conform/data/sys/ipc.h-data (ipc_perm.mode): Likewise.
	* conform/data/sys/sem.h-data (semid_ds.sem_nsems): Likewise.
	* conform/data/sys/socket.h-data (msghdr.msg_iovlen): Likewise.
	(msghdr.msg_controllen): Likewise.
	(cmsghdr.cmsg_len): Likewise.
	* conform/data/utmpx.h-data (utmpx.ut_tv): Likewise.
	* conform/Makefile (test-xfail-XPG3/sys/ipc.h/conform): Remove
	variable.
	(test-xfail-XPG3/sys/sem.h/conform): Likewise.
	(test-xfail-XPG4/stropts.h/conform): Likewise.
	(test-xfail-XPG4/sys/ipc.h/conform): Likewise.
	(test-xfail-XPG4/sys/sem.h/conform): Likewise.
	(test-xfail-XPG4/sys/socket.h/conform): Likewise.
	(test-xfail-UNIX98/stropts.h/conform): Likewise.
	(test-xfail-UNIX98/sys/ipc.h/conform): Likewise.
	(test-xfail-UNIX98/sys/sem.h/conform): Likewise.
	(test-xfail-UNIX98/sys/socket.h/conform): Likewise.
	(test-xfail-XOPEN2K/stropts.h/conform): Likewise.
	(test-xfail-XOPEN2K/sys/ipc.h/conform): Likewise.
	(test-xfail-XOPEN2K/sys/sem.h/conform): Likewise.
	(test-xfail-XOPEN2K/sys/socket.h/conform): Likewise.
	(test-xfail-XOPEN2K/utmpx.h/conform): Likewise.
	(test-xfail-POSIX2008/fcntl.h/conform): Likewise.
	(test-xfail-POSIX2008/stropts.h/conform): Likewise.
	(test-xfail-XOPEN2K8/fcntl.h/conform): Likewise.
	(test-xfail-XOPEN2K8/stropts.h/conform): Likewise.
	(test-xfail-XOPEN2K8/sys/ipc.h/conform): Likewise.
	(test-xfail-XOPEN2K8/sys/sem.h/conform): Likewise.
	(test-xfail-XOPEN2K8/sys/socket.h/conform): Likewise.