9term, acme: autoscroll

Ignore scroll/noscroll window setting.
Instead, scroll when the write begins in
or immediately after the displayed window content.

In the new scrolling discipline, executing
"Noscroll" is replaced by typing Page Up or
using the mouse to scroll higher in the buffer,
and executing "Scroll" is replaced by typing End
or using the mouse to scroll to the bottom of
the buffer.

R=r, r2
http://codereview.appspot.com/4433060

src/cmd/acme/exec.c

@@ -960,6 +960,7 @@ sendx(Text *et, Text *t, Text *_0, int _1, int _2, Rune *_3, int _4)
 	if(textreadc(t, t->file->b.nc-1) != '\n'){
 		textinsert(t, t->file->b.nc, Lnl, 1, TRUE);
 		textsetselect(t, t->file->b.nc, t->file->b.nc);
+		textshow(t, t->q1, t->q1, 1);
 	}
 }