Martin, jhawk and everyone,
	I release a modified version of the patch.
It implements a per screen scrollbuffer and corrects
the "beginning of line missing character" reported.
I definitely agree that having a per screen scrollbuffer
is the most sensible behaviour :)

As Martin Husemann suggested the scrollbuffer is only 
allocated once the screen scrolls out.
The small space waste of the previous implementation
(a 4096 page per 80x25 screen) has been removed.

There are also two feature that have not been implemented:
"trailing space at the end of line" compression and
euristic to share a common buffer in between screen
according to proportional scroll load.

Even if IMO these are very good ideas, I tend to believe 
that this two systems would add too much
complexity to the code without any real benefit since
the memory usage is not so high to justify them.

Always waiting for your feedback
	Thanks
		Paolo