_ioperm support for Arm

[Florian Weimer]

* Adhemerval Zanella:

> Also, from previous Cauldron discussion, we should make the deprecation
> in longer phases.  It also seems that compiler warning that symbol will
> be deprecated in future releases is not a complete way to warn developers
> to add configure build options take this consideration (the libgo example
> with uname come to my mind). So maybe we use a different strategy for
> sysctl, by deprecating in 2/3 releases and make it a compat symbol after
> 3/4 releases.

I think the ustat business was due to the fact that we did *not* issue a
warning beforehand.  Like sysctl, the deprecation is mainly captured in
the manual page for the system call.

The linker warnings happen only on some architectures right now (which
use the “generic” Linux system call ABI).

Once we've settled the ioperm matter for Arm, I will try to come up with
a simple patch that adds deprecation warnings for sysctl.

Thanks,
Florian