Check whether skipping the root element of a document's filename succeeded and use the filename itself if not (e.g. on relative filenames, #2702844).
Use the locale encoded filename when saving session files.

git-svn-id: https://geany.svn.sourceforge.net/svnroot/geany/trunk@3652 ea778897-0a13-0410-b9d1-a72fbfd435f5