fetchpatch is fetchurl that determinizes the patch.
Some parts of generated patches change from time to time, e.g. see #1983 and
http://comments.gmane.org/gmane.linux.distributions.nixos/12815
Using fetchpatch should prevent the hash from changing.
Conflicts (auto-solved):
pkgs/development/libraries/haskell/gitit/default.nix
Added BNFC-meta, alex-meta, and happy-meta.
Moved these tools into the tool section of haskell-packages.nix, and
paid special attention to the intended alphabetic order.
svn path=/nixpkgs/trunk/; revision=28506