gnu: Fix (evaluation of the) call to forceSystem.
Partially revert 7a45996 some more.

Removing more references to the non-existent license "stdenv.lib.licenses.perl5".
Thanks to @FlashKorten for catching those.
libtoxcore: Update to latest Git master.

The GitHub repository has changed the name to "toxcore".
Also indented buildInputs/configureFlags a bit less messy.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
libtoxcore: Add libopus and libvpx to buildInputs.

Those are necessary to do audio/video calls, which I guess is the whole
point of the Tox project.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
libtoxcore: Enable and fix up running test suite.

We not only require libcheck but also needed to disable a few tests,
without providing the former, test cases were signalled as being run
successfully but weren't actually run.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
toxic: Update to latest upstream Git master.

Unfortunately they've changed their build system to be makefile-only and
they don't seem to include test cases in the CLI anymore, so we needed
to adapt accordingly. Also added freealut and openal to the buildInputs,
in order to allow audio support.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
freealut: Clean up expression and add meta.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Upgrade docker to 1.1.2 and add docker module

This version of module has disabled socketActivation, because until
nixos upgrade systemd to at least 214, systemd does not support
SocketGroup. So socket is created with "root" group when
socketActivation enabled. Should be fixed as soon as systemd upgraded.

Includes changes from #3015 and supersedes #3028
initrd: Include filesystem support for /nix, /var etc.