Undocumented predicates

The following predicates are exported, but not or incorrectly documented.

 xref_uses_file(Arg1, Arg2, Arg3)

 xref_called(Arg1, Arg2, Arg3, Arg4, Arg5)

 xref_module(Arg1, Arg2)

 xref_op(Arg1, Arg2)

 xref_defined(Arg1, Arg2, Arg3)

 xref_definition_line(Arg1, Arg2)

 xref_called(Arg1, Arg2, Arg3, Arg4)

 xref_option(Arg1, Arg2)

 xref_prolog_flag(Arg1, Arg2, Arg3, Arg4)

 xref_source(Arg1)

 xref_source(Arg1, Arg2)

 xref_called(Arg1, Arg2, Arg3)

 xref_exported(Arg1, Arg2)

 xref_used_class(Arg1, Arg2)

 xref_hook(Arg1)

 xref_meta(Arg1, Arg2)

 xref_defined_class(Arg1, Arg2, Arg3)

 xref_meta(Arg1, Arg2, Arg3)

 xref_source_file(Arg1, Arg2, Arg3, Arg4)

 xref_public_list(Arg1, Arg2, Arg3, Arg4, Arg5, Arg6, Arg7)

 xref_public_list(Arg1, Arg2, Arg3, Arg4)

 xref_public_list(Arg1, Arg2, Arg3, Arg4, Arg5, Arg6)

 xref_source_file(Arg1, Arg2, Arg3)

 xref_done(Arg1, Arg2)

 xref_clean(Arg1)

 xref_current_source(Arg1)

 xref_comment(Arg1, Arg2, Arg3, Arg4)

 xref_public_list(Arg1, Arg2, Arg3)

 xref_mode(Arg1, Arg2, Arg3)

 xref_built_in(Arg1)

 xref_comment(Arg1, Arg2, Arg3)