Replace /rescue/vi with mined(1) from DragonFlyBSD

I have taken mined(1) from DragonFlyBSD and integrated into the
FreeBSD source tree.  This is a very lightweight full screen
editor with builtin support for cons25 and xterm.  Yes, it is
limited in its capabilites compared with /rescue/vi, but saves
use 360 kB of diskspace and it does not require a termcap file.
In replacing /rescue/vi, I have installed /bin/mined, /rescue/mined,
and /rescue/edit (as an alias to mined).  The installation into
/bin/mined is due to my limited understanding of the rescue/Makefile
structure.  If someone wants to eliminate /bin/mined, it's fine with
me.

Yes, I'm aware of PR bin/80256, but that appears to stalled in
a state of limbo.

I have a diff to src/bin and src/rescue if anyone is interested.

-- 
Steve