message: Add limit check in scroll_up/down_relative
diff: @@ -960,7 +960,8 @@ impl Term {
  /// Expects origin to be in scroll range.
  #[inline]
  fn scroll_down_relative(&mut self, origin: Line, lines: Line) {
  - trace!("scroll_down: {}", lines);
  + trace!("scroll_down_relative: origin={}, lines={}", origin, lines);
  + let lines = min(lines, self.scroll_region.end - self.scroll_region.start);
  // Copy of cell template; can't have it borrowed when calling clear/scroll
  let template = self.empty_cell;
  @@ -981,7 +982,8 @@ impl Term {
  /// Expects origin to be in scroll range.
  #[inline]
  fn scroll_up_relative(&mut self, origin: Line, lines: Line) {
  - trace!("scroll_up: {}", lines);
  + trace!("scroll_up_relative: origin={}, lines={}", origin, lines);
  + let lines = min(lines, self.scroll_region.end - self.scroll_region.start);
  // Copy of cell template; can't have it borrowed when calling clear/scroll
  let template = self.empty_cell;
  