A reduced set of Russian prompts
A new set of Russian test sentences
A new unified helper script preparing data for training a voice
Streamline handling of internal libraries
HTS Engine: detect endianness at runtime
NVDA synthDriver: do not use voice pairs to support automatic language
switching

The list of voices now contains only actual voices, and the driver now
supports the variant setting, which allows a user to select a second
voice for automatic switching between languages. We don't restrict the
language of the synthesizer to the language of NVDA anymore, and the
language of the current voice is reported to the screen reader.