Reduce buffer length to 50mS and don't override it when using eSpeak for audio.

CHANGELOG.md

 *  Fix determining the voice directory when installing the 32-bit Windows
    binaries on a 64-bit Windows system.
 *  Fix a regression with the saved parameter logic.
+*  Reduce the default buffer length to 50mS to improve latency.
+*  Don't override buffer length when using espeak-ng for audio.
 
 updated languages:
 

src/include/espeak-ng/speak_lib.h

    output: the audio data can either be played by eSpeak or passed back by the SynthCallback function.
 
    buflength:  The length in mS of sound buffers passed to the SynthCallback function.
-            Value=0 gives a default of 200mS.
+            Value=0 gives a default of 50mS.
             This paramater is only used for AUDIO_OUTPUT_RETRIEVAL and AUDIO_OUTPUT_SYNCHRONOUS modes.
 
    path: The directory which contains the espeak-ng-data directory, or NULL for the default location.

src/libespeak-ng/speech.c

 	my_audio = create_audio_device_object(device, "eSpeak", "Text-to-Speech");
 #endif
 
-	// buflength is in mS, allocate 2 bytes per sample
-	if ((buffer_length == 0) || (output_mode & ENOUTPUT_MODE_SPEAK_AUDIO))
-		buffer_length = 200;
+	// buffer_length is in mS, allocate 2 bytes per sample
+	if (buffer_length == 0)
+		buffer_length = 50;
 
 	outbuf_size = (buffer_length * samplerate)/500;
 	out_start = (unsigned char *)realloc(outbuf, outbuf_size);
 		outbuf = out_start;
 
 	// allocate space for event list.  Allow 200 events per second.
-	// Add a constant to allow for very small buf_length
+	// Add a constant to allow for very small buffer_length
 	n_event_list = (buffer_length*200)/1000 + 20;
 	espeak_EVENT *new_event_list = (espeak_EVENT *)realloc(event_list, sizeof(espeak_EVENT) * n_event_list);
 	if (new_event_list == NULL)