thunderbird/icedove packages up for test

[Guido Günther <agx@sigxcpu.org>]

Hi,
please give the thunderbird packages

    https://people.debian.org/~agx/icedove-lts/

a try. I'll add a new enighmail soonish since the current version
conflicts with the one in Wheezy.
Cheers,
 -- Guido