This makes the following changes:
1. setVoice takes a Voice object instead of a language string.
This is to make the API cleaner and allows SpeechSynthesis
to pass the correct parameter (identifier for SetVoiceByName,
or name for SetVoiceByProperties) to espeak.
2. The espeak_SetVoiceByName API is also exposed to support passing
the voice variant to use.
3. The age parameter has been re-added with the constants:
* SpeechSynthesis.AGE_ANY
* SpeechSynthesis.AGE_YOUNG
* SpeechSynthesis.AGE_OLD
based on the behaviour of the eSpeak voice selection algorithm.
NOTE: Due to the way that voice selection is implemented in eSpeak,
if variant is specified, the age and gender cannot be specified and
vice versa.
This renames `setVoiceByProperties` to the more consise `setVoice`
and removes the name parameter as this is not used -- the voice is
set by the language and gender parameters only.
The `age` parameter is not useful as eSpeak does not use this when
selecting voices. This is always set to `0` by TtsService.java.
The `variant` parameter is not used to select the actual voice
variant (from the `!v` directory) but to select the n^th matching
voice from the list of matching voices. This is always set to
select the first matching voice by TtsService.java.
Reece H. Dunn