Maintenance ending for glibc 2.17.

[Carlos O'Donell]

I'm no longer going to maintain glibc 2.17.

I thought I would have done some maintenance because
the branch is used by RHEL7, but given the semantics
of the RHEL release process it doesn't suit itself
well making this easy.

I'm going to focus my attention on 2.21 and 2.22
and the active branches used by Fedora and keeping
those maintained. And build up further the process
that Gentoo and Debian area already doing with their
distro branches.

Thanks to Mike for the recent backports to those
branches.

Cheers,
Carlos.