[Groff] Extending refer

[Bernd Warken]

The following extensions of refer exist in Heirloom and the known
refer history.

1) `refer.man' cites under `FILES':
file.i                   Index files.

But I couldn't find this file type and no documentation for them.

2) `refer.man' cites under `FILES':
/usr/dict/papers/Ind     Default database.

That file does not exist.  The directory for such a file should
be in the groff directory under /usr/local/share.

3) Moreover some `refer' database directory would be nice.

4) The programs in Heirloom and refer history
- addbib
- roffbib
- sortbib
might be useful as well.

Bernd Warken