* tta/C/main/manipulate_indices.c (setup_index_entries_sort_strings):
use a cast to convert char *to uint8_t * and avoid a useless copy
of the string.

* tta/C/main/manipulate_indices.c (setup_index_entries_sort_strings):
use locale variables for code clarity.

* tta/C/main/unicode.c (utf8_from_string, string_from_utf8): remove
comments, assume that casting is always a good way to convert between
char and uint8_t.