Here are two fixes for the ia32-compatibility mode handling
for the new semtimedop() system call for the ia64 architecture.

The first problem was that treatment of user-mode calls to semtimedop()
with a NULL 4th (struct timespec *) parameter was inconsistent with the
behavior of the same executable on i386 and also with a natively compiled
ia64 binary.  A NULL 4th arg to semtimedop() should result in no timeout
being used (like a straight semop() call) rather than in an EFAULT error.

The second problem was that a legitimate semtimedop() with a timeout was
also resulting in an EFAULT because the fetch of the internal timespec
strucure by sys_semtimedop() from semtimedop32()'s kernel stack was
treated as an invalid user-data reference.  This requires temporarily
switching the addressing limit with set_fs(), further requiring that
appropriate parameter checking by performed prior to the switch.

The const qualifier was removed from the (struct compat_timespec *) arg
to semtimedop32() so that the call to get_compat_timespec() wouldn't
generate a compilation warning.