Branched the 0.24 series, which will be maintained for a while to
support v1 git-annex repos, while main development moves to the 0.2011
series, with v2 git-annex repos.

git-annex 0.24 released with [[!toggle text="these changes"]]
[[!toggleable text="""
* Add Suggests on graphviz. Closes: #[618039](http://bugs.debian.org/618039)
* When adding files to the annex, the symlinks pointing at the annexed
  content are made to have the same mtime as the original file.
  While git does not preserve that information, this allows a tool
  like metastore to be used with annexed files.
  (Currently this is only done on systems supporting POSIX 200809.)"""]]