Remember the number of lines scrolled into the history (versus cleared

into the history) and when resizing only use scrolled lines and not
cleared lines (which are probably not intended to reappear). From
Chaoren Lin.

screen-write.c

@@ -1016,7 +1016,7 @@ screen_write_clearhistory(struct screen_write_ctx *ctx)
 	struct grid	*gd = s->grid;
 
 	grid_move_lines(gd, 0, gd->hsize, gd->sy);
-	gd->hsize = 0;
+	gd->hscrolled = gd->hsize = 0;
 }
 
 /* Write cell data. */