* tta/C/texi2any.c (main): set element_cdt_tree_fn to
html_element_cdt_tree if outputting HTML.

* tta/perl/Makefile.am (test_files),
tta/perl/t/input_files/customize_definition_index_translations.texi,
tta/perl/t/init_files_tests.t
(customize_definition_index_translations), tta/tests/Makefile.onetst,
tta/tests/customization/list-of-tests
(translated_strings_customization): move
customize_definition_index_translations Texinfo to the
customize_definition_index_translations.texi and use it for a test of
the command in tests/customization/list-of-tests.