my-env: Preserve http_proxy and ftp_proxy variables

There are few build scripts which set them to `nodtd.invalid` to disable
downloading files by buildscript. But for user environment we should
restore original values
Add `extraConfig` option for SLiM

so that various configuration options can be set without having to
expose every single configurable parameter
Merge pull request #3885 from suvash/feature/add-configuration-options-for-slim

Add `extraConfig` option for SLiM
Fix K3D build
Revert "Merge pull request #2449 from wkennington/master.grub"

This reverts commit 469f22d717e53c48d13a66ca862942e8098accc5, reversing
changes made to 0078bc5d8f87512104902eab00c8a44bef286067.

Conflicts:
	nixos/modules/installer/tools/nixos-generate-config.pl
	nixos/modules/system/boot/loader/grub/install-grub.pl
	nixos/release.nix
	nixos/tests/installer.nix

I tried to keep apparently-safe code in conflicts.
Revert "Fix syntax error in nixos/lib/build-vms.nix, introduced by 86c0f8c"

This reverts commit 704e91bab005eabe968a3b140222fb0cf7afd4db.
Revert "Merge pull request #3182 from wkennington/master.ipv6"

This reverts commit b23fd6585481a42937e105d5fce630a549900e86, reversing
changes made to 43654cba2c280ce17b81db44993d1c1bcae3a9c6.
add game 'tcl2048'
tcl2048: update to 0.2.6
tcl2048: wrong sha256sum.
grub: fix grub merge error
Merge pull request #3892 from robberer/bugfix/grub

grub: fix grub merge error
gource: update to version 0.42
Merge pull request #3893 from robberer/pkgs/gource

gource: update to version 0.42
Merge pull request #3889 from dbohdan/master

Added package tcl2048
haskell-xml-html-conduit-lens 0.3.2.0 -> 0.3.2.1
Bump snort and daq
pypyPackages.pycryptopp: mark as not supported on pypy
pythonPackages.cffi: 0.7.2 -> 0.8.6
PyPy ships with cffi, so don't use external cffi for packages