vt: expose system-wide UTF-8 default setting via sysfs

Create a variable, default_utf8, that defines the system-wide default UTF-8
setting.  This variable can be altered via sysfs. If the variable is properly
set, this should mimimize breakage of UTF-8 encoded consoles when doing a
reset or echo -e '\033c' and of newly opened/allocated consoles.

This is based from patches by Jan Engelhardt and Paul LeoNerd Evans.

Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Cc: Jan Engelhardt <jengelh@linux01.gwdg.de>
Cc: Paul LeoNerd Evans <leonerd@leonerd.org.uk>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>