Synopsis:
   clear [-all|-hidden|-visible] [-unhold]

Description:
   This command clears the current window of all text.  It is useful for
   wiping a screen that has rendered improperly (such as due to a bad
   termcap entry).

Options:
   -all      clears all windows, not just the current one
   -hidden   clears all hidden windows
   -visible  clears all visible windows
   -unhold   sets the window's HOLD_MODE off as well


