1: Added missing voice variants in the NVDA category including Iven 4, Steph, Steph 2 and Steph 3.
2: Completed the Persian translation.

This is caused by the Voice features being set to null. The fix in
Android Marshmallow is to make onGetFeaturesForLanguage return an
empty HashSet object. This does not work for eSpeak because:

  1.  eSpeak was overriding onGetVoices and initializing each Voice's
      features to null;

  2.  the bug is still present on Lollipop.

Thus, the fix here is two-fold:

  1.  make onGetVoices use onGetFeaturesForLanguage;

  2.  make onGetFeaturesForLanguage return an empty HashSet, so that
      eSpeak does not crash on Lollipop either.

When there is no TTS engine selected, mTts.getVoice() will throw
a NullPointerException. This is a workaround to cope with this bug
in Android.

This reverts commit 6ac54860a1.

This change was preventing the voice data from being installed.

The Android 5.0 Text-to-speech output settings dialog checks that
the languages from CheckVoiceData use the ISO3 language and
country codes. This change matches that expectation.

This improves the performance of looking up a voice by name.

As of Android 5.0, TextToSpeech.setLanguage calls the new
TextToSpeechService.onGetDefaultVoiceNameFor(lang,country,variant)
and uses the specified voice name.

The default Android 5.0 implementation of onGetDefaultVoiceNameFor
does not work with eSpeak. This provides a working implementation.

This fixes the TextToSpeechTest.testLanguages tests on Android 5.0.

The default Android 5.0 implementation enumerates the available
locales. This enumerates the voices returned by eSpeak.

This adds method declarations for the new voice APIs, forwarding
them to the default implementations.