my-env: pull --norc shell flag out into shell parameter

As zsh's corresponding flag is called --no-rcs, the build environment
couldn't be configured to use zsh at all.

Even then the custom PS1 won't work on zsh, but it's usable enough.

Close #1040.
Update fossil to 1.27, and enable the JSON API.
sauerbraten: SVN repository has moved
Add smlnj-110.76

Based on patch by Marc Weber:
http://lists.science.uu.nl/pipermail/nix-dev/2010-December/005625.html

Close #1058.
Merge branch 'fossil127' of https://github.com/linuxfood/nixpkgs