[det]el_history(+In:stream, 
?Action)Perform a generic action on the history. This provides an incomplete 
interface to history() from libedit. Supported actions are:
- clear
 - Clear the history.
 
- setsize(+Integer)
 - Set size of history to size elements.
 
- setunique(+Boolean)
 - Set flag that adjacent identical event strings should not be entered 
into the history.