Also, swap the logic around, to use less braces.

And which normally is just some ten or twenty characters long, and
never gets wildly overallocated.

But do it correctly this time: don't switch it on when replacing.

None of the prompts offer a total-refresh shortcut -- only the
edit window, the help viewer, and the file browser provide this.

There is no need for that -- it just causes flicker.

This fixes https://savannah.gnu.org/bugs/?49742.

Only when doing replacements does the edit window need a refresh: for
every new spotlight.  So, do the update request in the latter routine.

Mentioning "GNU nano" instead of "This program" and referring to the
website instead of to a postal address.

And remove a superfluous call.

The prompt has already been trimmed in do_prompt() to fit into the
available space.

Leave the optimization of actual screen writes to ncurses.

This fixes https://savannah.gnu.org/bugs/?48917.

This fixes https://savannah.gnu.org/bugs/?48916.

The $ sign looks too much like an S, and it "obscures" the answer by
being so "massive".  The < and > signs are lighter and work better.

This fixes https://savannah.gnu.org/bugs/?48894.

This fixes https://savannah.gnu.org/bugs/?48912.

This fixes https://savannah.gnu.org/bugs/?48796.

This fixes https://savannah.gnu.org/bugs/?48792.

This fixes https://savannah.gnu.org/bugs/?48852.

That is a task for the key-getting routine.

There is no need to specially flag a function key or editing key --
the keycode is indication enough in itself: outside of byte range.

Color-pair numbers and attributes can be OR'd together -- do so,
to save an attron() call whenever the hilite is on.

When we get a ^J as verbatim input, it is not possible to include it
into the file buffer or the prompt answer, because this would mean
adding an encoded null to the buffer or answer, and that is not what
the user intended.  One option would have been to simply ignore a ^J
in verbatim input.  But the choice has been made to act the same way
as when the ^J (0x0A) is found in the file data: start a new line.

That is the same response as to the Enter key, yes -- but the code
for the Enter key is ^M (0x0D), not ^J.  So, to be more precise,
rename the relevant variable from 'got_enter' to 'got_newline'.