[IA64] TS_RESTORE_SIGMASK

Replace TIF_RESTORE_SIGMASK with TS_RESTORE_SIGMASK and define
our own set_restore_sigmask() function.  This saves the costly
SMP-safe set_bit operation, which we do not need for the sigmask
flag since TIF_SIGPENDING always has to be set too.

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>