We should avoid defining color schemes that are unreadable on common
white-on-black or black-on-white terminals.  Change the black in the
autoconf error strings to brightred for that reason.

When probing symbols provided by ncurses, use the sublibs that pkg-config
reported in case they're needed (like when libtinfo is a sep library).

URL: https://savannah.gnu.org/bugs/?49614

In addition, tweak some of the wording.

Kind-of-discovered-by: Markus Bergholz <markuman@gmail.com>

Also when somehow key_defined() is missing.

This fixes https://savannah.gnu.org/bugs/?49614

.
Reported-by: Mike Frysinger <vapier@gentoo.org>

- make version highlight less blindly greedy and conform to real versions
- move version matching before USE matching to avoid hitting USE flags
  that look like versions
- change USE regex to match the Gentoo PMS
- extend arch match to include more keywords
- make category matching more restrictive to avoid false positives
- drop operators =< and => that Gentoo doesn't support

URL: https://savannah.gnu.org/bugs/?49569

Reported-by: Konstantin Shakhnov <kastian@mail.ru>

(Bug was introduced yesterday, by commit a4132e2e.)

Otherwise the user can override a 'set nowrap' in /etc/nanorc only
via the command line.

This fixes https://savannah.gnu.org/bugs/?49593 reported by Shirish.

This fixes the two bugs reported by Anton Minaev
in https://savannah.gnu.org/bugs/?49511.

This fixes https://savannah.gnu.org/bugs/?49530.

Also, don't use ignore-case for things that don't contain letters.

Also replace some backslashed spaces because they hinder the
justification of the man page.

Reported-by: Sumedh Pendurkar <sumedh.pendurkar@gmail.com>

This fixes https://savannah.gnu.org/bugs/?49467.

When giving a line number on the command line, do_gotolinecolumn() needs
to know the width of the screen to be able to (roughly) place the target
line in the center of the screen.

This fixes https://savannah.gnu.org/bugs/?49462.

This fixes https://savannah.gnu.org/bugs/?49423.

Also remove some cluttering conditional compilation.

Also, don't bother conditionalizing two booleans for the tiny version.

The nanorc option already exists, but not the corresponding one
for the command line.

This fixes https://savannah.gnu.org/bugs/?49428.

This make tiny nano slightly less tiny, but makes the code more readable.

It does not update anything -- it just picks a new point from
where to start displaying the buffer.  All actual updating of
the screen is done by edit_refresh() and edit_redraw() and such.

Also mention the corresponding toggle (M-#).

This fixes https://savannah.gnu.org/bugs/?49406.

There is no need to look at this for every painted line, because
the margin can only change when some key is struck.

Instead of doing this in two places: after interpreting shortcuts,
and after injecting characters.

To prevent the display from getting messed up, making nano unusable.