small
Simplification of various print APIs.

* [ASSOC_MULTI,PRINT_EXT,RDF_NAME,SC] Removed the explicit output argument from the debug predicates. This makes the APIs for printing much sparser. Calls to these predicates should use with_output_to/2 if output should be diverted.
* [PRINT_EXT,FIX] Added meta_predicate/1 directives for option lists, together with meta_options/3 calls at the beginning of every predicate that uses meta-options.
* [RDF_NAME,NEW] Added rdf_pair_name/1 for printing pairs of RDF terms.