bug#22873: Can we support multiple cursors?

[Keith David Bershatsky]

Thank you, Eli, for teaching me how to better use move_it_to.

In the tests that I ran today using:

move_it_to (&it, POS, -1, it.last_visible_y - 1, -1, MOVE_TO_POS | MOVE_TO_Y);

I observed that IT will stop at *the beginning of the last partially visible 
line* when POS is on the last partially visible line and POS's X coordinate is 
greater than 0.  IT does *not* stop at the window-end.

The following seems to work better when POS is on the last partially visible 
line and POS's x coordinate is greater than 0.

move_it_to (&it, POS, it.last_visible_x, it.last_visible_y - 1, -1, MOVE_TO_POS 
| MOVE_TO_X | MOVE_TO_Y);

I built a new working draft of Emacs based on the latter example and will be 
trying using it throughout the day.

Keith