Magic sysrq fails to work on many keyboards, particulary most of notebook
keyboards.  This patch fixes it.

The idea is quite simple: Discard the SysRq break code if Alt is still being
held down.  This way the broken keyboard can send the break code (or the user
with a normal keyboard can release the SysRq key) and the kernel waits until
the next key is pressed or the Alt key is released.
Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>