IMPORTANT: glibc security update

[Mark H Weaver <mhw@netris.org>]

Hello Guix!

I've pushed a fix for CVE-2015-7547 to the master branch, although Hydra
has not fully rebuilt it.  I directed Hydra to build the most popular
packages first, and with greater effort devoted to x86_64, so my hope is
that most of what typical desktop users need is already built on x86_64.
Still, it is likely that you'll need to compile some things locally.

i686 is not as fully built, so users will probably need to do some more
compiling, but hopefully it is manageable.  I was able to fully update
my Xfce desktop system on i686 anyway.

As I write this, the rebuilds of armhf and mips64el are considerably
less advanced, so be prepared for a significant amount of local
recompilation.

We'll prioritize getting grafts working properly soon, so that we can
deploy security updates to core libraries much more quickly in the
future.

     Thanks,
       Mark