Enforce that relative links are used within the page, so that local
installations don't require internet conection and/or don't redirect to
the web needlessly.
This is done by looking for any local link (barring exceptions) when
checking links with 'check-html-references.py'.
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>