[PATCH] add vt console scrollback ioctl

[PATCH] add vt console scrollback ioctl

From: Samuel Thibault <Samuel.Thibault@ens-lyon.fr>

There is no way for a braille device driven by brltty (userland root-owned
daemon) to scrollback the virtual console, the only way is to use the pc
keyboard.  A very simple TIOCLINUX ioctl meets this need (tested).

Also add a command for bringing the last console to the top, as keyboard.c's
lastcons() does when pressing alt - down arrow.