git mirror repacked, new branches

[Bernie Innocenti]

I repacked our (un)official git mirror (http://gcc.gnu.org/git) with 

 git repack -a -d -f --window=100 --depth=100 --window-memory=2g

The pack is now 600MB, which is a bit scary, but still manageable.
Mysteriously, cloning this repo yields a smaller pack of just 519MB,
which still contains all the branches. It was probably caused by entries
in the reflog, which I have now disabled.

As an additional bonus, I've added refs for all the current branches tom
make them visible in gitweb and easier to clone.

-- 
   // Bernie Innocenti - http://codewiz.org/
 \X/  Sugar Labs       - http://sugarlabs.org/