FR: tighter integration with occur

[aspiers]

M-s o for ctrlf-occur is a really nice feature; however it doesn't make usage of occur very convenient when the ctrlf minibuffer is active:

• The resulting *Occur* buffer is not updated in any way as the user navigates through the ctrlf matches. It would be cool if the point gets moved around the *Occur* buffer to correspond to the currently selected ctrl match.
• Once you hit Enter, the *Occur* buffer is immediately hidden, so if you want to (say) use occur-edit-mode, you have to unhide it again. It would be cool if there was a way to exit without hiding it.

[raxod502]

Yes, those changes both seem reasonable, as long as the implementation does not turn out to be obtusely complicated for some unexpected reason.