my-env/default.nix: fix "sdl-env" vs "env-sdl" typo

my-env/default.nix lists an example on how to create an SDL environment
that can be installed with "nix-env -i sdl-env". That is actually wrong
and will not work. The correct command is "nix-env -i env-sdl".
Merge pull request #333 from bjornfor/fix-typo

my-env/default.nix: fix "sdl-env" vs "env-sdl" typo
pkgs/build-support/cabal: filter internal 'testDepends' field from the expression to avoid unnecessary hash changes
pkgs/build-support/cabal: filter 'doCheck=false' field from the expression to avoid unnecessary hash changes

In the master branch, doCheck defaults to 'false', which means that no package
will change its hash unless its doCheck field is set to 'true' explicitly. In
the stdenv-updates branch, however, all Haskell packages have a default setting
of 'doCheck=true'. Once that branch has been merged, filtering doCheck is no
longer necessary.
pkgs/build-support/cabal: add 'testDepends' to 'extraBuildInputs' if 'doCheck' is set to 'true'
Re-generate all Haskell packages with the latest version of cabal2nix.

This change brings support for building and running the regressions test suites.
haskell-base-compat: add version 0.2.1
haskell-ChasingBottoms: add version 1.3.0.5
haskell-concurrent-extra: add version 0.7.0.5
haskell-data-accessor-transformers: add version 0.2.1.4
haskell-encoding: add version 0.6.7.2
haskell-file-location: add version 0.4.5.2
haskell-hspec-meta: add version 1.4.4
haskell-idna: add version 0.2
haskell-lockfree-queue: add version 0.2
haskell-markdown-unlit: add version 0.2.0.1
haskell-nanospec: add version 0.1.0
haskell-network-transport-tests: add version 0.1.0.1
haskell-punycode: add version 2.0
haskell-stringbuilder: add version 0.4.0