followup on polishing FreeBSD port

See https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=190667#c10 for
another problem, maybe solved with a ".if exists(${PERL5})" condition.
CORS handling: allow more URLs

Allow also requests from bbbike.de and bbbike.org (previously only
localhost), and enable it for json and geojson output formats
(previously only xml).

Including new test script cgi-cors.t.