Hachoir is incompatible with urwid >= 0.9.8

[2254] fixes a first bug. Known remaining bugs:

• display not refreshed in most cases
• exception on '-' & '+' keys:

    ...
    File "/var/lib/python-support/python2.4/urwid/curses_display.py", line 202, in run_wrapper
      return fn()
    File "/home/jm/hachoir/trunk/hachoir-urwid/hachoir_urwid/urwid_ui.py", line 655, in run
      canvas = top.render(size, focus=True)
    File "/var/lib/python-support/python2.4/urwid/widget.py", line 121, in finalize_render
      canv = fn(self, size, focus=focus)
    File "/var/lib/python-support/python2.4/urwid/listbox.py", line 339, in render
      raise ListBoxError, "Focus Widget %s at position %s within listbox calculated %d rows but rendered %d!"% (`focus_widget`,`focus_pos`,focus_rows, focus_canvas.rows())
  urwid.listbox.ListBoxError: Focus Widget <hachoir_urwid.urwid_ui.Tabbed object at 0x2ab249138d90> at position 0 within listbox calculated 72 rows but rendered 73!
  

[2282] fixes the exception on '-' & '+' keys.

[2283] fixes the last known bug.

Strangely, urwid 0.9.8 is slightly slower than 0.9.7.2.