Rectangular regions

[Stefan Monnier]

I've installed earlier today a patch which adds basic support for
rectangular regions.  The entry point currently is `M-x rectangle-mark'.
Besides making commands aware of rectangular regions (currently only
things like C-w, M-w, C-y, and M-y pay attention to the shape of the
region), I have one main UI issues: provide a key binding for
rectangle-mark.

Maybe we could also push the design a bit further and provide shorter
key-bindings in "rectangular region mode" (no, it's not a mode
currently) to access string-rectangle and open-rectangle, but for now,
the main issue is how to quickly start selecting a rectangle.
I.e. a good key binding for rectangle-mark.

A related issue is to find a mouse-binding for it.


        Stefan