Enable some features for RTEMS in libstdc++

Enable some features for RTEMS in libstdc++

Remove RTEMS support from crossconfig.m4 since this code is not used due to
"with_newlib" being "yes".

libstdc++-v3/ChangeLog:

	* configure: Regnerate.
	* configure.ac (newlib, *-rtems*): Enable TLS support for all RTEMS
	targets except bfin, lm32, mips, moxie, or1k, and v850.
	For all RTEMS targets, define HAVE_ALIGNED_ALLOC, HAVE_AT_QUICK_EXIT,
	HAVE_LINK, HAVE_POLL, HAVE_QUICK_EXIT, HAVE_READLINK, HAVE_SETENV,
	HAVE_SLEEP, HAVE_SOCKATMARK, HAVE_STRERROR_L, HAVE_SYMLINK,
	HAVE_TRUNCATE, and HAVE_USLEEP.
	* crossconfig.m4 (*-rtems*): Remove.