Define more termios.h macros unconditionally for alpha (bug 21277).

Define more termios.h macros unconditionally for alpha (bug 21277).

termios.h should define IUCLC for UNIX98 and older XSI standards.  The
sysdeps/unix/sysv/linux/alpha version defines it only if __USE_MISC,
so causing some conform/ tests to fail.

Other versions define it unconditionally (I* being a reserved
namespace for this header); the API should be consistent between
architectures in the absence of a clear reason for it to differ (and
given that a symbol is part of the API on two architectures, I don't
see any reason for the feature test macros required ever to differ
between those architectures), so this patch makes the alpha version
define it unconditionally as well.  Two non-POSIX macros alongside it,
IMAXBEL and IUTF8, are also defined unconditionally on other
architectures, so this patch makes them consistent by defining them
unconditionally on alpha as well.

Tested (compilation only) with build-many-glibcs.py.

	[BZ #21277]
	* sysdeps/unix/sysv/linux/alpha/bits/termios.h (IUCLC): Define
	unconditionally.
	(IMAXBEL): Likewise.
	(IUTF8): Likewise.