When interrupted by a signal, a wait operation on a gated monitor
should not be restarted automatically from kernel space, but reported
to the user instead.

Rationale: the mutex guarding the monitor was dropped prior to
waiting, and must be re-acquired explicitly by an UNWAIT request when
the interrupted status is detected from user-space. Consequently, we
cannot retry a WAIT request without transitioning to user-space first.

Add the T_NORST local information bit to the thread control block,
which is set by the monitor wait operation, and tested by the syscall
trampoline code for disabling automatic restart.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>