fixup: pygobject rename pth
pygtk in pythonPackages, checks disabled, demo works, relates #223

Previously the checkPhase was not executed. It is now and a couple of
issues with it are seded away.
Fix compliation of gts on Darwin
Merge branch 'master' of github.com:NixOS/nixpkgs
don't put propagated recursivePthLoader into pth file, #257
graphviz: Fix compilation on darwin
Update x86info description. Add Homepage.
urxvt-9.16
Merge remote-tracking branch 'upstream/master' into master_clean
Merge branch 'master_clean' of https://github.com/jcumming/nixpkgs into master_clean
imagemagick: disable ghostscript on darwin, to make it work
Add the replace-dependency build support function.

The use case is to do a deep replacement of a dependency without rebuilding the entire tree.
For example, suppose a security hole is found in glibc and a patch released. Ideally, you'd
just rebuild everything, but that takes time, space, and CPU that you might not have, so in
the mean time you could build a safe version of, say, firefox with:

  firefox-safe = replace-dependency { drv = firefox; old-dependency = glibc; new-dependency = patched-glibc; };

Building firefox-safe will rebuild glibc, but only do a simple copy/string replacement on all other dependencies
of firefox. On my system (MBP 13" mid-2012), after a new glibc had been build building firefox took around 11 seconds.

See the comments in the file for more details.
Merge pull request #259 from jcumming/urxvt.130111

urxvt-9.16
Remove some artifacts of a failed attempt from replace-dependency
replace-dependency: Don't strictly require that drv, old-dependency, and new-dependency be derivations
replace-dependency: Better function names
Fix mit-scheme

These changes are necessary for me to use mit-scheme on i686 NixOS.
mit-scheme in the current state should be broken on x86_64 either and
these changes should fix, too. I however did not test this.
Merge pull request #254 from jcumming/x86info.130109

X86info.130109
haskell-cipher-aes: update to version 0.1.7
haskell-cprng-aes: update to version 0.3.4