* tta/perl/Texinfo/Convert/HTML.pm (_convert_printindex_command),
tta/perl/Texinfo/Convert/HTMLNonXS.pm (_prepare_index_entries_targets)
(output_internal_links), tta/perl/Texinfo/Convert/LaTeX.pm
(_index_entry), tta/perl/Texinfo/Convert/Plaintext.pm
(process_printindex), tta/perl/Texinfo/Indices.pm
(index_entry_first_letter_text_or_command)
(setup_index_entries_sort_strings), tta/perl/Texinfo/IndicesNonXS.pm
(index_entry_element_sort_string): set debug argument of
index_content_element, add debug argument and set argument of
index_entry_first_letter_text_or_command and
index_entry_element_sort_string.

* tta/perl/Texinfo/Convert/HTML.pm,
tta/perl/Texinfo/Convert/HTMLNonXS.pm,
tta/perl/Texinfo/Convert/Plaintext.pm: use intermediary variable for
DEBUG to avoid calling get_conf too often.