Fix TextToSpeech,setLanguage on Android 5.0.

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.

android/src/com/reecedunn/espeak/TtsService.java

 
     @Override
     public String onGetDefaultVoiceNameFor(String language, String country, String variant) {
-        return super.onGetDefaultVoiceNameFor(language, country, variant);
+        final int result = onLoadLanguage(language, country, variant);
+        switch (result) {
+            case TextToSpeech.LANG_MISSING_DATA:
+            case TextToSpeech.LANG_NOT_SUPPORTED:
+                return null;
+        }
+        return mMatchingVoice.name;
     }
 
     @Override