Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

The idea of mapping non-existen characters to space (0x20) was nice alone,
but those maps also used as backward maps for Paste, so space becomes mapped
to last non-existen character on Paste as result.

Fix it by mapping non-existen characters to another non-existen one, i.e. to
0x00, so unused 0x00 can be backward-mapped to some junk without real harm.

Pointed by: Alexander Kabaev <ak03@gte.com>

1) Map all unused characters into 'space'.
2) iso-8859-4_to_cp437 not do what its name tells at all, remove it

Improve Greek support in syscons

PR: 32119
Submitted by: Basileios Anastasatos <B.Anastasatos@MyRealBox.com>