switch_to_tt and switch_to_skas to the
top level _switch_to function, keeping us from duplicating code.  It is
required for the stack trace patch to work properly.

Signed-off-by: Allan Graves <allan.graves@gmail.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
"UíZš0x