Fix -Wunused-parameter warnings.

src/libespeak-ng/speech.c

 
 ESPEAK_NG_API espeak_ng_STATUS espeak_ng_InitializeOutput(espeak_ng_OUTPUT_MODE output_mode, int buffer_length, const char *device)
 {
+	(void)device; // unused if HAVE_PCAUDIOLIB_AUDIO_H is not defined
+
 	my_mode = output_mode;
 	out_samplerate = 0;
 

tests/ssml-fuzzer.c

 static int initialized = 0;
 
 static int SynthCallback(short *wav, int numsamples, espeak_EVENT *events) {
-	/* prevent warning for unused arguments */
-	(void) wav;
-	(void) numsamples;
-	(void) events;
+	(void)wav; // unused
+	(void)numsamples; // unused
+	(void)events; // unused
 
 	return 0;
 }
 
 extern int LLVMFuzzerInitialize(const int* argc, char*** argv)
 {
+	(void)argc; // unused
 	filepath = dirname(strdup((*argv)[0]));
 	return 0;
 }