This call was used to update the written sample count used by
wave_get_remaining_time. As that function has been removed, this
code is no longer needed.

This logic was implemented to limit the number of audio events sent
to a device, but the logic is not too relevant in practice (these
calls return 0 most of the time), and the logic is broken (e.g. when
calling Synthesize with a very long block of text).

This function call does not affect the audio output in non-async
modes. Audio output in that case is handled within the SynthOnTimer
helper function.

New vowel definitions, fixes in rules and voice intonation.