> > With this ok jtt@, but it'd be nice to have another dev's input
> > regarding the bundled regex library and compilation warnings.

committed with small tweaks;

- don't get fancy with regex for SITES, a fixed string is just fine and
has some advantages

- add comment with github url (often helpful when checking updates)

regarding regex; seems upstream has some issues with newer versions and
it is probably not the only copy of ancient versions of gnu regex in
ports. maybe upstream will pick up https://github.com/ge-ne/bibtool/pull/96
which should fix some of this..