sys: Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

Implement ECMA-48 "REP", some Linuxen have started emitting them recently.

Approved by: ed

teken, vt(4): Parse the "Cursor style" escape sequence

The escape sequence (e.g. `^[[2 q`) was unsupported before and the
letter `q` was displayed as a typed character. The sequence is used by
Neovim for instance.

Now, it is properly parsed. However, it is ignored, so it won't change
the cursor style.

Because the escape sequence contains a space character, the
`gensequences` script had to be modified to support that. In the
`sequences` file, a space is represented as the string `SP`.

Fix various whitespace inconsistencies in sys/teken.

A new jail(8) with a configuration file, to replace the work currently done
by /etc/rc.d/jail.

Move libteken out of the syscons directory.

I initially committed libteken to sys/dev/syscons/teken, but now that
I'm working on a console driver myself, I noticed this was not a good
decision. Move it to sys/teken to make it easier for other drivers to
use a terminal emulator.

Also list teken.c in sys/conf/files, instead of listing it in all the
files.arch files separately.