Fix termios.h XCASE namespace (bug 19925).

bits/termios.h (various versions under sysdeps/unix/sysv/linux)
defines XCASE if defined __USE_MISC || defined __USE_XOPEN.  This
macro was removed in the 2001 edition of POSIX, and is not otherwise
reserved, so should not be defined for 2001 and later versions of
POSIX.  This patch fixes the conditions accordingly (leaving the macro
defined for __USE_MISC, so still in the default namespace).

Tested for x86_64 and x86 (testsuite, and that installed shared
libraries are unchanged by the patch).

	[BZ #19925]
	* sysdeps/unix/sysv/linux/alpha/bits/termios.h (XCASE): Do not
	define if [!__USE_MISC && __USE_XOPEN2K].
	* sysdeps/unix/sysv/linux/bits/termios.h (XCASE): Likewise.
	* sysdeps/unix/sysv/linux/mips/bits/termios.h (XCASE): Likewise.
	* sysdeps/unix/sysv/linux/powerpc/bits/termios.h (XCASE):
	Likewise.
	* sysdeps/unix/sysv/linux/sparc/bits/termios.h (XCASE): Likewise.
	* conform/Makefile (test-xfail-XOPEN2K/termios.h/conform): Remove
	variable.
	(test-xfail-XOPEN2K8/termios.h/conform): Likewise.