Some commits wrt atom feed

[Andreas Zwinkau]

Hello,
we have been using a modified version of cgit and we wanted to share
our changes, so hopefully they can be included into upstream.

I rebased them all to a clean branch on Github:
  https://github.com/qznc/cgit/compare/omaster...clean

They all affect the Atom feed. Fixing validation errors, including a diff, etc.

-- 
Andreas Zwinkau

work email: zwinkau at kit.edu
private email: qznc at web.de
homepage: http://beza1e1.tuxen.de