Hey Guix,

here's a few small patches for messaging.scm:

#1 - A copyright notice.
#2 - An update for c-toxcore to 0.1.10.
#3 - Add filteraudio to qtox inputs.
#4 - Add python2-axolotl to gajim inputs (needed for the OMEMO plugin).
#5 - An update for prosody to 0.10.0.