This implements using the new ptrace option SYSEMU_SINGLESTEP in UML
(advanced sysemu) in SKAS and TT modes.
To have a fast selection of the appropriate ptrace option to use next,
a 2 dimensional arry is used and singlestepping() is modified to return
0,1 or 2:
    0 = don't do singlestepping
    1 = singlestep a syscall
    2 = singlestep a "non syscall" instruction

In do_syscall() writing of the syscall number is supressed, if the
advanced sysemu is in use (that does it itself).
Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>