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

Merge VT(9) project (a.k.a. newcons).

Reviewed by: nwhitehorn
MFC_to_10_after: re approval

Sponsored by: The FreeBSD Foundation

o Implement history buffer.
o Join history buffer with screen buffer. Same type of things.
o Reimplement buffer as an array of rows. Make it circular, so no overflow
tracking.
o Implement VT_PROCESS mode. Locking of VT switching by owner process.
o Add debug and deadtimer sysctls. deadtimer - defaulting to 15 seconds, time
to wait process answer in VT_PROCESS mode, to do VT switch in case when
process hang.
o Implement later console attach.
o Fix (partially yet) keyboard allocation.
o Add drivers priority. Disallow to replace KMS driver with VGA.
o Add ability to resize terminals.

Sponsored by: The FreeBSD Foundation

Readd the vt(4) driver and corresponding tools.