Add system.replaceRuntimeDependencies to quickly replace system dependencies
nixos-build-vms: Fix function invocation to test driver
Add vtop, update some node packages.
postfix-211: Update from 2.11.0 to 2.11.1
tinc: Update from 1.0.23 to 1.0.24
Merge pull request #2837 from lethalman/security

Add system.replaceRuntimeDependencies to quickly replace system dependencies
ghc-head: update to version 7.9.20140608