This was becoming heavy to manage.

This is the first commit I do entirely in VE. It's a habit I'm planning
on taking as it helps a lot to find usability issues.

Previously, it would keep the old buffer displayed why typing over
it. I had kept it thus because I didn't want to erase the buffer
right away because the behavior is that when we type nothing, we
keep the buffer as-is and repeat the action.

Now, the behavior of I and F is much better. It keeps the buffer
displayed until the first non-return keystroke and then erases it.

Also, fixed PSP leak in _type and fixed PSP overuse in successful
_F (they balanced out).

Also, made LIST properly handle full 64-chars lines not ending with
a null or CR. Previously, such a line would be accompanied by its
following line, duplicating that line's output.

Also, add word "C!+" and fix PSP leak in FILL.