pkgs/build-support/cabal: set LANG="en_US.UTF-8" for the Haddock run

Haskell packages that contain non-ascii characters in their .cabal file
or somewhere else in their haddock documentation fail to compile under
nixpkgs and usually flagged with noHaddock = true. I wanted to do the
same for modularArithmentic, when I realized that we just have to set
the locale to some UTF-8 compatible locale in build-support/cabal to fix
this issue correctly.
haskell-bytestring-progress: re-enable haddock documentation
haskell-diagrams: re-enable haddock documentation
haskell-multirec: re-enable haddock documentation
haskell-wxc: re-enable haddock documentation
Merge branch 'origin/master' into stdenv-updates.
pkgs/build-support/cabal: add support for running specific tests only via 'testTarget'

The dns packages requires this feature, because it ships two test programs: one
of them requires network access (so we cannot run it), but the other test does
not. Setting testTarget appropriately allows us to run only one of the two
suites.
haskell-dns: run only the 'spec' test suite, the 'network' test suite won't succeed on Hydra
xz: Update to 5.0.5
bash: Update to 4.2-p45
less: Update to 458

For some crazy reason, less is a stdenv dependency.
ed: Update to 1.9
dbus_cplusplus: fix build with gcc>=4.7, via Gentoo patch
coin3d: fix build with newer gcc
wesnoth: fix build, minor update, parallel builds

Yes, games are the most important things in nixpkgs...
not that I actually plan to play it anytime soon ;-)
perl: disable tests on Darwin, refactor stdenv.lib usage

There was a mysterious error, which I don't have resources to investigate:

Removing test lib/Net/hostent.t
sed: -i: No such file or directory
mu: fix build by using older texinfo
v8: fix build with newer gcc
Merge tag 'bluenix/goal' into stdenv-updates2
add "quilt" (patch manager)