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

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

MFC 219886, 226100, 226111, 226341, 242529, 259015, 259016, 259019, 259049,
259071, 259102, 259110, 259129, 259130, 259178, 259179, 259203, 259221,
259261, 259532, 259615, 259650, 259651, 259667, 259680, 259727, 259761,
259772, 259776, 259777, 259830, 259882, 259915, 260160, 260449, 260450,
260688, 260888, 260953, 261269, 261547, 261551, 261552, 261553, 261585
o Merge vt(4) virtual terminal (a.k.a. newcons) to stable/9.
o Merge teken updates.
o Add few more tty methods required by vt(4).
o Update syscons(4) to work with fresh teken.

Sponsored by: The FreeBSD Foundation

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

Approved by: re (implicit)

Fix various whitespace inconsistencies in sys/teken.

Add proper build infrastructure for teken.

I'm not sure whether we should install teken as a library on any stock
FreeBSD installation, but I can imagine people want to tinker around
with it now and then. Create a /sys/teken/libteken, which holds a
Makefile to install a shared library version of the terminal emulator,
complete with a manpage.

Also add Makefiles for the demo/stress applications, to build it against
the shared library.