realtime signals corrupted by pause() on ia64

[Roland McGrath]

> It is a glibc bug on ia64, which exists on at least glibc-2.2.4-30 and
> glibc-2.2.4-31 (RH AS 2.1).

We are not considering glibc-2.2.x bug reports here any more, only report
for 2.3.1 and later.  You should report that using redhat's bugzilla for AS2.1.

The mapping of int signal masks to sigset_t is correct.  It's just that
going through the int format is wrong, and in 2.3.x pause no longer does that.

The current pause function is buggy in that it in fact unblocks all
signals.  We will fix that.