Backport of ubuntu-keyring to wheezy-backports

[Andrew Bradford <andrew@bradfordembedded.com>]

Hi backports list,

I have backported the ubuntu-keyring package from Jessie to wheezy-backports.  I've uploaded it to Debian Mentors at [1] and the dsc file is at [2].  If anyone is able to review this for me and upload it, I would greatly appreciate it!

[1]: http://mentors.debian.net/package/ubuntu-keyring
[2]: http://mentors.debian.net/debian/pool/main/u/ubuntu-keyring/ubuntu-keyring_2012.05.19-1~bpo70+1.dsc

I often use Ubuntu releases with debootstrap so having Ubuntu signing keys in my wheezy would all validation of downloaded Ubuntu debs and I also found closed bug #457899 [3] asking for inclusion of this package into Debian.

[3]: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=457899

This package is not in Wheezy so I have not included changelog entries besides my backport entry.  Hopefully this is OK.
If there's any other way I can improve my backport, please let me know!

Thanks!
-Andrew