nixos: Try to show an helpful message when the user sets config. or options.

Feel free to improve or remove :-)
pbzip2: update package
lbzip2: add package
gitolite: add dataDir
Merge pull request #4773 from abbradar/gitolite-home

gitolite: 'dataDir' option
leiningen: remove clojure dependency
Merge pull request #4771 from abbradar/pbzip2-update

pbzip2: update package
Bump git-repo to 1.21

Still no versioned URL, but there’s been a new release. SHA1 pulled
from http://source.android.com/source/downloading.html#installing-repo.
Merge pull request #4775 from ajbouh/master

Bump git-repo to 1.21
pidgin-latex: replace with SF one and fix
monthly bump of dolphinEmuMaster

also dolphinEmu and dolphinEmuMaster had an extraneous stdenv removed
from buildInputs
Merge pull request #4776 from abbradar/pidgin-latex

pidgin-latex: replace with SF one and fix
nixos/modules/services/monitoring/graphite.nix: don't create graphite user unconditionally

I'm not sure what exactly this user is needed for, i.e. under what circumstances
it must exist or not, but creating it unconditionally seems like the wrong thing
to do. I complained to @offlinehacker about this on Github, but got no response
for a week or so. I'm disabling the extraUsers bit to put out the fire, and now
hope that someone who actually knows about Graphite implements a proper solution
later.
nixos/modules/services/monitoring/graphite.nix: strip trailing whitespace
nix-prefetch-git: fix determinism with leaveDotGit

Add more files to the delete list:

 * .git/FETCH_HEAD
 * .git/ORIG_HEAD
 * .git/refs/remotes/origin/HEAD
 * .git/config

Further, remove all remote branches, remove tags not reachable from the
given 'rev', do a full repack and then garbage collect unreferenced
objects.

According to my testing, the result is fully deterministic. As in "any
change done to the upstream repo, ahead of 'rev', will not affect the
hash of the resulting 'clone'". Even changing the clone URL will not
change the output hash, because .git/config is removed.

A new version of git can of course change store format, but that's
unavoidable.

For big repositories, the repack operation may be a bit heavy. But as
far as I can see there is no cheaper way to determinism.
sudo: allow adding extra configuration options to the bottom of sudoers

from sudoers (5):
When multiple entries match for a user, they are applied in order.
Where there are multiple matches, the last match is used (which is not necessarily the most specific match).
r-RcppArmadillo: fix download URL
r-nloptr: add missing dependency on nlopt library
r-PoweR: fix build
postgris: 1.5.1 -> 1.5.8, fixes #3389