[PATCH] vgacon: Add support for soft scrollback

The scrollback buffer of the VGA console is located in VGA RAM.  This RAM
is fixed in size and is very small.  To make the scrollback buffer larger,
it must be placed instead in System RAM.

This patch adds this feature.  The feature and the size of the buffer are
made as a kernel config option.  Besides consuming kernel memory, this
feature will slow down the console by approximately 20%.

Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: Jindrich Makovicka <makovick@kmlinux.fjfi.cvut.cz>
Cc: Martin Mares <mj@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>