code cleanup: fix -Wunused-variable

src/libespeak-ng/fifo.c

 		i++;
 
 		struct timespec ts;
-		struct timeval tv;
 
 		clock_gettime2(&ts);
 
 		       && errno == EINTR)
 			continue;
 
-		assert(gettimeofday(&tv, NULL) != -1);
-
 		if (err == 0)
 			a_start_is_required = true;
 	}

src/libespeak-ng/intonation.c

 {
 	PHONEME_LIST *p;
 	int ix;
-	int count_stressed = 0;
 	int final_stressed = 0;
 
 	int tone_ph;
 	for (ix = 0; ix < n_phoneme_list; ix++, p++) {
 		if ((p->type == phVOWEL) && (p->stresslevel >= 4)) {
 			final_stressed = ix;
-			count_stressed++;
 		}
 	}
 

src/libespeak-ng/numbers.c

 	int value;
 	int subtract;
 	int repeat = 0;
-	int n_digits = 0;
 	char *word_start;
 	int num_control = 0;
 	unsigned int flags[2];
 		else
 			acc += prev;
 		prev = value;
-		n_digits++;
 	}
 
 	if (IsDigit09(word[0]))

src/libespeak-ng/speech.c

 	// Fill the buffer with output sound
 	int length;
 	int finished = 0;
-	int count_buffers = 0;
 
 	if ((outbuf == NULL) || (event_list == NULL))
 		return ENS_NOT_INITIALIZED;
 		event_list[event_list_ix].unique_identifier = unique_identifier;
 		event_list[event_list_ix].user_data = my_user_data;
 
-		count_buffers++;
 		if ((my_mode & ENOUTPUT_MODE_SPEAK_AUDIO) == ENOUTPUT_MODE_SPEAK_AUDIO) {
 			finished = create_events((short *)outbuf, length, event_list);
 			if (finished < 0)