Add libgit2, pygit2 and powerline beta
updated firmware-linux from 0.36-to-0.38
mercurial: Update to 2.6.1

Also, set a default for web.cacerts so that the system certificates on
NixOS are used.
cacert: Update to 20121229
linux: Re-enable the memory resource controller

We accidentally lost this in Linux >= 3.5 because the kernel options
were renamed.  (Probably an argument for not using "?" in the kernel
config...)
Merge pull request #519 from offlinehacker/powerline2

Add powerline beta, libgit2 and pygit2
Merge pull request #527 from qknight/firmware-linux-0.36-to-0.38

updated firmware-linux from 0.36-to-0.38
let hydra mirror unfree firmware
pg8000: upgrade to 1.09 to support postgresql 9.1/9.2
Add curlOpts parameter to the fetchurl function