Fix some glitches in inset-select-all

Fix a crash reported in #7727. This happened because cur.pos() was reset before cur.pit(). In this case, cur.lastpos() will usually be wrong.

Fix bad behaviour when selecting at top level with several paragraphs.

Update documentation.
Merge remote-tracking branch 'github/build-bot-master' into bleeding-edge-master
2014.11.14-10.00