Allow the user to execute commands at the beginning of the X session.

The difference between xsession and xprofile is that xsession is exec'd and xprofile is sourced.
So with xprofile all commands after sourcing will still be exectued. This allows for instance
autostarting of applications while configuring the start of a window manager via configuration.nix.
haskellPackages.dbmigrations: New expression
Update Io lang to version 2013.12.04
Update HOL Light to revision 179
Update PolyML to version 5.5.1
qjackctl: add meta.platforms
drumkv1: update from 0.3.5 to 0.3.6

http://monitor.nixos.org/patch?p=drumkv1&v=0.3.6
haskell-blaze-markup: update to version 0.5.2.1
haskell-ghc-mod: update to version 3.1.5
haskell-shelly: update to version 1.4.1
haskell-snap-core: update to version 0.9.6.0
haskell-snap-server: update to version 0.9.4.0
haskell-snap: update to version 0.13.2.0
haskell-wai-extra: update to version 2.0.2
haskell-warp-tls: update to version 2.0.1
haskell-warp: update to version 2.0.2
Allow specifying extra qemu flags using QEMU_OPTS. Replace CentOS 6.3 with CentOS 6.5 (6.3 is removed from site).
haskellPackages.websocketsSnap: New exppression
haskellPackages.httpStreams: New expression
Add kmscon, a kms-based replacement for kernel VTs

Note that currently this depends on the default nixpkgs mesa and pango.
It may be possible to build more limited versions that don't e.g. depend
on the full X stack without limiting kmscon (which of course doesn't use
X).

Depends on libtsm, added in the same commit.

Signed-off-by: Shea Levy <shea@shealevy.com>