Add poppler_document_build_dests_tree() to glib frontend

I'd like to enumerate PDF named destinations in a PDF. From poppler 0.48.0, C++ API that can do it has been added. ( 99267c0b , 15171597 )

But, GLIB API has not yet been merged. I've created the patch for current master branch.

This merge request is related to issue #472 .