The $doc stuff needed changes, probably because of ghostscript newly
reacting to some configure flags that stdenv passes.
- share/ghostscript/9.22/doc was an ugly location for documentation,
and I didn't like their new share/ghostscript/9.24 either,
so that got changed to share/doc/ghostscript/9.24
- their process no longer installs examples, apparently,
but I don't expect that would be any problem for us