uml: xterm driver tidying

Major tidying of the xterm console driver:
	got rid of the tt-mode gdb support
	tidied up the includes
	fixed lots of style violations
	replaced os_* calls with glibc calls in xterm.c
	all printk calls now have a severity indicator
	the error paths of xterm_open are closer to being right

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>