P_PSKOLEM_CONV takes two arguments.  The first is a variable f, which
must range over functions of the appropriate type, and the second is a term of
the form !p1...pn. ?q. t (where pi and q may be pairs).  
Given these arguments, P_PSKOLEM_CONV returns the theorem:
   |- (!p1...pn. ?q. t) = (?f. !p1...pn. tm[f p1 ... pn/q])