Synopsis:
   set underline_video [on|off|toggle]

Description:
   When turned on, the client will permit underlined text to be displayed.
   The ^U (control-u) character is used to switch underlining on and off.
   When turned off, the ^U will appear as a U.

See Also:
   bind(4) blink, bold, highlight_off, reverse, underline;
   set(4) blink_video, bold_video, reverse_video, underline_video