The SetAttr hack used to be needed because the hostname was part of the
Attr, and was required to be present. Now that it's moved to Host, let's
get rid of that, since it tended to waste CPU.
This is to work around OSX's brain-damange regarding filename case
insensitivity.
Avoided moving config.hs, because it's a config file. Put in a symlink to
make build work.
Joey Hess