Update ProofGeneral to version 4.2
ProofGeneral: remove dead code (compatibility with emacs 23).
Revert "chromium-25.0.1364.172, 26.0.1410.40, 27.0.1448.0"

This reverts commit 6617f5ca9e92f307c468018a7d05c8c080c5441e.

The old situation was definitely better. Sorry for waiting so long for
the revert.
mongodb: upgrade to 2.4.0
Merge pull request #407 from maggesi/proofgeneral_updates

Update ProofGeneral to version 4.2
haskell-cuda: add version 0.5.0.1
haskell-circle-packing: add myself as maintainer
haskell-hakyll: update to version 4.2.2.0
rsync: add meta.license attribute
rsync: fix build an FreeBSD (by disabling ACL support)
gnumake: disable test suite on FreeBSD

One test fails, unfortunately, but I'm not sure what to do about it.
libxslt: fix impurity on 'native-stdenv' platforms

libxslt has optional dependencies which may be found in /usr or
/usr/local on platforms that have a native stdenv. With those features
enabled, the build generated binaries that depend on libraries outside
of the store. In this particular case, the NixOS channel had binaries
for FreeBSD that depended on libgcrypt, apparently because that packages
happens to be installed outside of Nix on the build machine. On other
machines, however, those binaries failed with unresolvable references.
git: fix build on FreeBSD

Our hard-linking code depended on md5sum, which FreeBSD doesn't have in its
system environment. To avoid that impure dependency, the hard-linking is now
done with the 'hardlink' utility from Nixpkgs.
libxslt: revert impurity fix on 'native-stdenv' platforms

Commit 16863d8ffe24649fb6a7500f2b457dd2e559de47 caused massive re-builds.
This change needs to be made differently.
libxslt: fix impurity on 'native-stdenv' platforms

libxslt has optional dependencies which may be found in /usr or
/usr/local on platforms that have a native stdenv. With those features
enabled, the build generated binaries that depend on libraries outside
of the store. In this particular case, the NixOS channel had binaries
for FreeBSD that depended on libgcrypt, apparently because that packages
happens to be installed outside of Nix on the build machine. On other
machines, however, those binaries failed with unresolvable references.
haskell-HGL: drop obsolete library that doesn't compile anymore with recent GHCs
haskell-xdot: jailbreak to fix build with recent versions of polyparse
Add renameutils package.
Update bitcoin-qt to 0.8.1
Adding Steam Locomotive, for the fun