Also when toggling the help lines back on or the extra editing space
back off, keep the cursor near the bottom of the screen if it /was/
there, instead of centering it -- if smooth scrolling is on, that is.

This supplements the fix for https://savannah.gnu.org/bugs/?50933.

When the editing space gets narrower, either by toggling line numbers on
or making nano's window smaller, and when the cursor is near the bottom,
it can be pushed offscreen.  In that case, don't get it back onscreen by
centering the current line but by putting it on the bottom row.  This
makes for a smoother experience.

This fixes http://savannah.gnu.org/bugs/?50933.

And hide the cursor again as soon as the user scrolls.
Achieve this through making the 'didfind' variable global.

Also, remove a superfluous call of wnoutrefresh(), as bottombars()
already does that.

This fixes https://savannah.gnu.org/bugs/?50918

.
Reported-by: David Lawrence Ramsey <pooka109@gmail.com>

Also, trim some comments and avoid an unused-variable warning.

Also, reshuffle two initializations to go sit with the other ones.

The bottomwin has just been refreshed by update_the_statusbar(),
and it should not be the responsibility of the prompt routines
to keep the edit window up to date, as they don't write anything
there.

Things have morphed over time and display_buffer() no longer actually
displays the buffer -- it just displays the title bar, precalculates
the multiline color info, and schedules a refresh of the edit window.

Also, avoid an unused-variable warning when configured with
--enable-tiny --enable-help --enable-multibuffer.

Searching for an empty string should be impossible, it should never
happen, but it is bit too hard to verify this at the moment.

If the length of the haystack is smaller than the length of the needle,
this means that also the length of the tail will be smaller -- because
pointer will be bigger than or equal to haystack -- so the pointer gets
readjusted to be a needle length before the end of the haystack, which
means that it ends up /before/ the haystack: thus the while loop will
never run.

On average, this saves some 200 nanoseconds per line.

Because it is slightly faster.

It is not an index, it is not an offset from anything,
it is a direct pointer.

And because I think it looks slightly better.

This avoids https://savannah.gnu.org/bugs/?49912 while at the same time
avoiding to draw the edit window twice in a row -- the first drawing
would use a wrong margin, which results in a visible and irritating
shift left or right of the content upon the second drawing.

This fixes https://savannah.gnu.org/bugs/?50877.

We should measure the length of each /translated/ shortcut description,
not of the original English one.

This fixes https://savannah.gnu.org/bugs/?50899.

This addresses https://savannah.gnu.org/bugs/?50897

.
Reported-by: Hannu Nyman <hannu.nyman@iki.fi>

This elides a counter and a comparison from the central loop,
and thus makes the search a tiny bit faster.

And one-letter variables I cannot "see" -- they are too small.

An iterator should not be called "start_col", because it is only the
starting column at the very beginning.

Also, start_col (after the rename) can never be /larger/ than column.

The mbwidth() function itself checks whether UTF-8 is being used
and does the right thing.

Backspace is a more logical counterpart of Space than minus.

Also, harmonize some configure-option descriptions,
add a slash after a subdir, and fix a typo.

Also, add two missing configure options, and frob some other things.

It complained of "Unbound key" until now.

That is: nest the conditions consistently.
And in the bargain rename the variable.

Also, mention that help texts can now be searched through, update
a copyright notice, and update and simplify a copyright year.

And in the process transform the token DISABLE_HELP to ENABLE_HELP.

This avoids applying the default syntax, or the syntax specified
with --syntax, to a ^G help text.