* tta/C/main/document.c (document_sorted_indices_by_index)
(document_sorted_indices_by_letter)
(print_document_indices_sort_strings),
tta/perl/Texinfo/DocumentNonXS.pm
(print_document_indices_sort_string),
tta/perl/XSTexinfo/parser_document/DocumentXS.xs
(print_document_indices_sort_strings): remove unused converter
arguments.  Update callers.

* tta/perl/t/test_utils.pl (test): remove use of a converter for
a print_document_indices_sort_strings call with converter, as it is
not possible anymore.

* tta/perl/Texinfo/Convert/Converter.pm
(_converter_indices_sort_strings): rename
converter_indices_sort_strings as _converter_indices_sort_strings.

* tta/perl/Texinfo/DocumentNonXS.pm (document_indices_sort_strings),
tta/perl/XSTexinfo/parser_document/DocumentXS.xs: put
setup_indices_sort_strings code in document_indices_sort_strings and
remove setup_indices_sort_strings, since it is not called anymore.

* tta/C/convert/texinfo.h, tta/swig/texinfo.i: remove
STTF_setup_index_entries_sort_strings now that it has no effect.
Update users.