new_binder : string * hol_type -> unit
!x:bool. (x=T) \/ (x=F)
$! (\x. (x=T) \/ (x=F))
   - new_theory "anorak";
   > val it = () : unit
   - new_binder ("!!", (bool-->bool)-->bool);
   > val it = () : unit
   - Term `!!x. T`;
   > val it = `!! x. T` : term