url-mode: store absolute row numbers in start/end coordinates

This allows us to update the jump label positions when the viewport
changes.

This in turn allows us to stay in URL mode while the user is using the
mouse to scroll in the scrollback history.

Scrolling with the keyboard is currently not possible, since input
handling in URL mode does not recognize “regular” key bindings. We
_could_ add scrollback up/down bindings to URL mode too, but lets not,
for the time being.

(Note: an alternative to this patch is to disallow mouse scrolling
too. Then we could have kept the URL start/end as viewport local
coordinates).

commands.c

@@ -83,6 +83,7 @@ cmd_scrollback_up(struct terminal *term, int rows)
     } else
         term_damage_view(term);
 
+    render_refresh_urls(term);
     render_refresh(term);
 }
 
@@ -157,5 +158,6 @@ cmd_scrollback_down(struct terminal *term, int rows)
     } else
         term_damage_view(term);
 
+    render_refresh_urls(term);
     render_refresh(term);
 }