FIXED: exporting predicates in presence of exported operators

FIXED: exporting predicates in presence of exported operators

* sweep.pl (sweep_exportable_predicates/2): new predicate.
* sweeprolog.el (sweeprolog--module-term)
(sweeprolog--exportable-predicates)
(sweeprolog-analyze-start-exportable)
(sweeprolog-analyze-fragment-exportable): no longer used, deleted.
(sweeprolog-exportable-predicates): new function.
(sweeprolog-read-exportable-predicate): use it.
(sweeprolog-export-predicate): handle exported operators.