Fix bug 3303 from Bernhard Roider. Some explanation:

Fix bug 3303 from Bernhard Roider. Some explanation:

The problem was that pit is a reference to cur.pit() and was set to lastpit() + 1 before calling recordUndo(cur, ...). thus an invalid cursor position was stored in the undo buffer.
A side effect of the attached patch is that now the cursor keeps staying in the moved section header  on undo (which is not the case in current trunk)

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@17410 a592a061-630c-0410-9148-cb99ea01b6c8