code cleanup: pass voice_t wvoice as a parameter instead of using a global

SetSynth_Klatt() was using wvoice in two ways:
1) global wvoice was used directly
2) global wvoice was also passed in Wavegen_Klatt() as an argument "v"

Now the code only uses the function argument wvoice

Contributes to #68.

src/libespeak-ng/klatt.c

@@ -838,14 +838,13 @@ static double DBtoLIN(long dB)
 	return (double)(amptable[dB]) * 0.001;
 }
 
-extern voice_t *wvoice;
 static klatt_peaks_t peaks[N_PEAKS];
 static int end_wave;
 static int klattp[N_KLATTP];
 static double klattp1[N_KLATTP];
 static double klattp_inc[N_KLATTP];
 
-int Wavegen_Klatt(int length, int resume, frame_t *fr1, frame_t *fr2, WGEN_DATA *wdata)
+int Wavegen_Klatt(int length, int resume, frame_t *fr1, frame_t *fr2, WGEN_DATA *wdata, voice_t *wvoice)
 {
 	if (resume == 0)
 		SetSynth_Klatt(length, fr1, fr2, wvoice, 1);
@@ -937,7 +936,7 @@ int Wavegen_Klatt(int length, int resume, frame_t *fr1, frame_t *fr2, WGEN_DATA
 	return 0;
 }
 
-static void SetSynth_Klatt(int length, frame_t *fr1, frame_t *fr2, voice_t *v, int control)
+static void SetSynth_Klatt(int length, frame_t *fr1, frame_t *fr2, voice_t *wvoice, int control)
 {
 	int ix;
 	double next;
@@ -1007,9 +1006,9 @@ static void SetSynth_Klatt(int length, frame_t *fr1, frame_t *fr2, voice_t *v, i
 	nsamples = length;
 
 	for (ix = 1; ix < 6; ix++) {
-		peaks[ix].freq1 = (fr1->ffreq[ix] * v->freq[ix] / 256.0) + v->freqadd[ix];
+		peaks[ix].freq1 = (fr1->ffreq[ix] * wvoice->freq[ix] / 256.0) + wvoice->freqadd[ix];
 		peaks[ix].freq = (int)peaks[ix].freq1;
-		next = (fr2->ffreq[ix] * v->freq[ix] / 256.0) + v->freqadd[ix];
+		next = (fr2->ffreq[ix] * wvoice->freq[ix] / 256.0) + wvoice->freqadd[ix];
 		peaks[ix].freq_inc =  ((next - peaks[ix].freq1) * STEPSIZE) / length;
 
 		if (ix < 4) {

src/libespeak-ng/klatt.h

@@ -179,7 +179,7 @@ typedef struct {
 
 void KlattInit(void);
 void KlattReset(int control);
-int Wavegen_Klatt(int length, int resume, frame_t *fr1, frame_t *fr2, WGEN_DATA *wdata);
+int Wavegen_Klatt(int length, int resume, frame_t *fr1, frame_t *fr2, WGEN_DATA *wdata, voice_t *wvoice);
 
 #ifdef __cplusplus
 }

src/libespeak-ng/wavegen.c

@@ -1346,7 +1346,7 @@ static int WavegenFill2()
 			wdata.n_mix_wavefile = 0; // ... and drop through to WCMD_SPECT case
 		case WCMD_KLATT:
 			echo_complete = echo_length;
-			result = Wavegen_Klatt(length & 0xffff, resume, (frame_t *)q[2], (frame_t *)q[3], &wdata);
+			result = Wavegen_Klatt(length & 0xffff, resume, (frame_t *)q[2], (frame_t *)q[3], &wdata, wvoice);
 			break;
 #endif
 		case WCMD_MARKER: