www/hs-gitit: Restore and update to 0.15.1.1

Gitit is a wiki program written in Haskell. It uses Happstack for the
web server and pandoc for markup processing. Pages and uploaded files
are stored in a git, darcs, or mercurial repository and may be
modified either by using the VCS's command-line tools or through
the wiki's web interface. By default, pandoc's extended version of
markdown is used as a markup language, but reStructuredText, LaTeX,
HTML, DocBook, or Emacs Org-mode markup can also be used. Gitit can
be configured to display TeX math (using texmath) and highlighted
source code (using highlighting-kate).

Other features include

• plugins: dynamically loaded page transformations written in Haskell (see "Network.Gitit.Interface")
• categories
• caching
• Atom feeds (site-wide and per-page)
• a library, "Network.Gitit", that makes it simple to include a gitit wiki in any happstack application

WWW: https://github.com/jgm/gitit

PR: 273260