Code checked for both langopt LOPT_IT_DOUBLING and attribe $double.
LOPT_IT_DOUBLING is redundant. $double already has a test in
dictionary.test

Code had a check for tr->langopts.param[LOPT_IT_DOUBLING] & 2 but that bit value is
not used in any language. That logic was removed.

Note: Strange that FLAG_ALT7 is used but ALT4-ALT6 are not. Same with
R6p.

utf8_nbytes() is only used in dictionary.c. Others are moved to common.c

It's used only in readclause.c

TODO: Rename so the meaning of the function is easier to understand.

This first reverts "Fix number_buf buffer overflow"
(commit ada93e2db0)

This for loop is apparently actually expected to to skip over NUL
characters.

Fixes #1302

Instead, this limits number processing to 32 digits, as break_numbers does
not support more and would provide bogus result with further digits.

Also fix the signedness of break_numbers so that the 32th bit
actually effectively works.

With emojis, phoneme strings can be very long

TranslateWord2 passes translator2 as tr to TranslateWord which may call
TranslateWord3, SpeakIndividualLetters, TranslateLetter, which was calling
SetTranslator2 again, thus freeing the very tr being used. Make that
latter use another translator.

Found by parsing the results from this bash script:
for define in $(grep define *.h |  awk'{print $2}');
do if ! grep -q $define *.c
then
        echo "$define not found";
fi
done

It is not used by any language. There is no need to check for it in
LoadVoice().

The #defines should be renamed to better convey their meaning.

The flag is never set anywhere so the if-clause will always evaluate to false.

When set in a language file, a period followed by a lower case letter is
detected as end of sentence. Normal behavior is to require a capital
letter.

- param2[] is only used to set a second value to LOPT_BRACKET_PAUSE. It is simpler
to have two values in param[] instead. This simplifies the codebase.

- Instead of setting "option bracket X Y" in language files, use
keywords "brackets X" and "bracketsAnnounced Y" instead to follow the
naming convention of other keywords.

- Add missing documentation to docs/voices.md.

There is no code related to it.

It is set but never used.

translate.h gives two settings to LOPT_CAPS_IN_WORD, but only one of them is actually ever used.

It's a duplicate of CTRL_EMBEDDED.

It is set in voices.c but never used. docs/voices.md indicates that the keyword intonation only takes one parameter, confirming that option_tone2 is unused.