Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Convert {small prefix}BSD to TERM=xterm as well.

Clean up the ttys files shipped with PicoBSD, NanoBSD and TinyBSD. While
there, it seems one of them still had references to sio(4). Make it in
sync with what we do in the base system.

In the spirit of nanoBSD and PicoBSD, add TinyBSD.
Submitted by jmeloatfreebsdbrasil,com-br
(Jean Milanez Melo)
As PicoBSD becomes slightly less useful, TinyBSD fills the gap below nanoBSD.