Fix focusing editor on notebook tab click.
Minor formatting and use NZV, DOC_FILENAME macros.
Make doc_at() debug function check idx is within range.


git-svn-id: https://geany.svn.sourceforge.net/svnroot/geany/branches/document-pointer@2702 ea778897-0a13-0410-b9d1-a72fbfd435f5