And in the bargain avoid a duplicate call of strlenpt(prompt).

The interval 2013-2017 for the Free Software Foundation is valid
because in those years there were releases with changes by either
Chris or David, and the GNU maintainers guide advises to mention
a new year in all files of a package, not just in the ones that
actually changed, and be done with it for the rest of the year.

Verify at startup that the number is not too small.

Rename some variables in the process, and remove two cluttering asserts.

These improvements will eventually make do_home() and do_end() take
parameters.  Since the global function lists can hold only functions
without parameters, preemptively add do_home_void() and do_end_void(),
and make the global function lists use them.

Most of these variables are freed moments later -- reallocating
them is thus a waste of time.

The conditionalizing saved negligible amounts of space, of memory, and
of speed.

This disallows entering a verbatim ^J (0x0A) when typing text or
search terms, and disallows a verbatim ^@ (0x00) when typing a
filename.  Nano beeps when the disallowed code is attempted.

This addresses https://savannah.gnu.org/bugs/?49897.

A KEY_WINCH does not need to be separately treated since the basic
action for anything that is not recognized at the yes-no prompt is:
to continue.

Also at the yes-no prompt, a 0x0A byte should be displayed as a ^J
instead of splitting the prompt bar in two and spreading it over
two lines.

This fixes https://savannah.gnu.org/bugs/?49934.

And certainly don't return zero when the key wouldn't have been found,
because that would have meant jumping a word to the right.

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.