IceCat-68.2.0-guix0-preview1 is now available on master

[Mark H Weaver]

Hello fellow Guix,

I'm pleased to announce that IceCat-68.2.0-guix0-preview1 is now on the
'master' branch, and that substitutes for x86_64-linux are available
from ci.guix.gnu.org.

This update includes fixes for CVE-2019-11757, CVE-2019-11759,
CVE-2019-11760, CVE-2019-11761, CVE-2019-11762, CVE-2019-11763,
CVE-2019-11764, and CVE-2019-15903.

Note that IceCat 68 has not yet been released by the IceCat project.
This is a work-in-progress, and may not currently meet the
privacy-respecting standards of the IceCat project.

I encourage you all to try it and report back with your experiences.

     Thanks,
       Mark