Due to #19 the GDAL-configuration GML_SKIP_RESOLVE_ELEMS was set to HUGE
when the user requests resolving of xlink:href (previously NONE).
This change is presumably the reason for problems reported resolving in #25.
Since probably not everyone will be satisified with one or other of the
options then the user should be able to choose which to use once
resolving of xlink:href is activated, thus removing the need for the devloper
to decide which option to use and passing this decision to the user.
The default GML_SKIP_RESOLVE_ELEMS is maintained as HUGE.