(split) Readd the vt(4) driver and corresponding tools.
(split) Merge in FreeBSD HEAD r226141.
(split) Sync with head@234197

Ok'd by: ed
(split) IFC @ 243795
(split) IFC @ 247036
(split) MFC@r248830

Approved by:	ed (project owner)
(split) MFC @r219886.
(split) MFC @r254374.
(split) MFC @r256148.
(split) MFC @r256953
(split) MFC @r256964.
(split) MFC @r257698.
(split) MFC @r257740.
(split) MFC @r258091.
(split) MFC @r258947.

Sponsored by:	The FreeBSD Foundation
(split) Remove daft KASSERT.
(split) Cosmetic changes.
(split) Replace the magic numbers with something more readable.
(split) Add support for the MediaTek/Ralink RT5572 chipset.
Committed over the TP-LINK TL-WDN3200 (RT5572) on amd64 with WPA.

While here, add my copyright.
(split) Fix compilation when the "USB_DEBUG" option is set.