Parallel building is enabled again in GHC 7.6.2, because we hope the issues
we've had with earlier versions have been remedied. If anyone experiences build
errors with this package, please file issue at Github!
ghc-7.6.2: cosmetic, no functional change
Hide package sets for GHC 6.10.4, 6.12.3, 7.0.4, 7.4.1, and 7.6.1 from nix-env
(and from Hydra). It is still possible to install any of those packages by
referring to them by attribute:

 | $ nix-env -iA haskellPackages_ghc6104.hopenssl --dry-run
 | (dry run; not doing anything)
 | installing `haskell-hopenssl-ghc6.10.4-1.6.1'
 | these paths will be fetched (50.61 MiB download, 450.34 MiB unpacked):
 |   /nix/store/rjsgga1fdqin47n2rkfn9l7v9ncsfh9l-haskell-hopenssl-ghc6.10.4-1.6.1
 |   /nix/store/y567qhqbjxbkldg3kq2clzn52a56cmdn-haskell-mtl-ghc6.10.4-1.1.0.2
 |   /nix/store/zbn24z1443fbrx6ch1nn2vnss9bdw1g0-ghc-6.10.4

It's no longer possible to install those by name anymore, though:

 | $ nix-env -i haskell-hopenssl-ghc6.10.4
 | error: selector `haskell-hopenssl-ghc6.10.4' matches no derivations

That style works only for active GHC versions 7.4.2 and 7.6.2:

 | $ nix-env -qaP \* | grep  haskell-hopenssl
 | haskellPackages.hopenssl                          haskell-hopenssl-ghc7.4.2-1.6.1
 | haskellPackages_ghc742_no_profiling.hopenssl      haskell-hopenssl-ghc7.4.2-1.6.1
 | haskellPackages_ghc742_profiling.hopenssl         haskell-hopenssl-ghc7.4.2-1.6.1-profiling
 | haskellPackages_ghc762.hopenssl                   haskell-hopenssl-ghc7.6.2-1.6.1

These changes intend to ease the load on Hydra. If you desperately need
pre-build binaries of any of those old versions, please post a short note
on the nix-dev mailing list.
all-packages.nix: fix typos in the haskellPackages attribute sets for GHC 7.4.2

The haskellPackages_ghc742_{no_,}profiling set accidentally referred to
the GHC 7.4.1 versions.