InetURLObject class does not work correctly with internal document
links, containing not full url, but just a fragment. This case added
as an exception for HTML link export.

Change-Id: I44496a1cf186836d4194fc65ce7bf9aeb2f79b65
Reviewed-on: https://gerrit.libreoffice.org/17993Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>
Tested-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>