Support deterministic PRNG mode in CLI

src/espeak-ng.c

     "-x\t   Write phoneme mnemonics to stdout\n"
     "-X\t   Write phonemes mnemonics and translation trace to stdout\n"
     "-z\t   No final sentence pause at the end of the text\n"
+    "-D\t   Enable deterministic random mode\n"
     "--compile=<voice name>\n"
     "\t   Compile pronunciation rules and dictionary from the current\n"
     "\t   directory. <voice name> specifies the language\n"
 	int phoneme_options = 0;
 	int option_linelength = 0;
 	int option_waveout = 0;
+	bool deterministic = 0;
 	
 	espeak_VOICE voice_select;
 	char filename[200];
 	option_punctlist[0] = 0;
 
 	while (true) {
-		c = getopt_long(argc, argv, "a:b:d:f:g:hk:l:mp:qs:v:w:xXz",
+		c = getopt_long(argc, argv, "a:b:Dd:f:g:hk:l:mp:qs:v:w:xXz",
 		                long_options, &option_index);
 
 		// Detect the end of the options.
 		case 'd':
 			strncpy0(devicename, optarg2, sizeof(devicename));
 			break;
+		case 'D':
+			deterministic = 1;
+			break;
 		case 'h':
 			printf("\n");
 			PrintVersion();
 		exit(1);
 	}
 
+	if (deterministic) {
+		// Set random generator state to well-known
+		espeak_ng_SetRandSeed(1);
+	}
+
 	if (option_waveout || quiet) {
 		// writing to a file (or no output), we can use synchronous mode
 		result = espeak_ng_InitializeOutput(ENOUTPUT_MODE_SYNCHRONOUS, 0, devicename[0] ? devicename : NULL);