nixos: allow adding extra modules through environment

This is useful for adding extra functionality or defaults to _every_
nixos evaluation.

My use case is overriding behaviour for all nixos tests, for example
setting packageOverrides to newer versions and changing some default
dependencies/settings.

By making this accessible through an environment variable, this can now
be fully accomplished externally. No more need to fork
nixos/nixpkgs (which becomes a maintenance burden), just use the channel
instead and plug in via this envvar.
Merge pull request #5358 from bluescreen303/nixos-extra-modules

nixos: allow adding extra modules through environment
gsutil: add crcmod to dependencies. Needed to download from Google Storage.
Added mirrors for MySQL.
emacs24Packages.haskellMode updated to latest git.
Merge pull request #5367 from aycanirican/master

emacs24Packages.haskellMode updated to latest git.
Disable fontconfig tests: they break after Freetype security update, and apparently we get something working regardless of the test problems
Some lua and awesome improvements

- Move lgi to luaPackages
- Use luaPackages in awesome and passthru lua
- Allow to pass lua modules to the awesome WM so that those can be used in the configuration
e19: update enlightenment core libraries
e19: fix - not showing keyboard layouts - issue
docker: update from 1.3.1 to 1.3.3, potentially fixes CVE-2014-6407, CVE-2014-6408
nodejs: update from 0.10.32 to 0.10.33, potentially fixes CVE-2014-7192
icecast: update from 2.4.0 to 2.4.1, potentially fixes CVE-2014-9018
nixos/tests/gitlab.nix: set TimeoutStartSec to 10min

(cherry picked from commit 5bafb9cf0fea00470be4ff9b342849339297eeb4)
Signed-off-by: Domen Kožar <domen@dev.si>
It is called Dingo! yes, Dingo!
Remove udev from /run/opengl-drivers

/run/opengl-drivers should contain only libGL-related libraries, not
stuff like udev. Injecting anything into LD_LIBRARY_PATH is dangerous
because it can break applications that expect a different version of
the library.

Caused by eef9a8ac2a30b495ff7184382ed0dbd73b3b88e4. Fixes #5371.
Merge branch 'mysql-mirrors' of https://github.com/fmapfmapfmap/nixpkgs
firefox-wrapper: more gstreamer plugins

The previous commit effaa51 broke some of soundcloud in firefox.
owncloud-client: added meta.platforms = stdenv.lib.platforms.uniq;
owncloud-client: added meta.platforms = stdenv.lib.platforms.unix;