Add PRNG and use it instead of rand()

src/libespeak-ng/common.c

 	return ucd_tolower(c);
 }
 
+static uint32_t espeak_rand_state = 0;
+
+long espeak_rand(long min, long max) {
+	// Ref: https://github.com/bminor/glibc/blob/glibc-2.36/stdlib/random_r.c#L364
+	espeak_rand_state = (((uint64_t)espeak_rand_state * 1103515245) + 12345) % 0x7fffffff;
+	long res = (long)espeak_rand_state;
+	return (res % (max-min+1))-min;
+}
+
+void espeak_srand(long seed) {
+	espeak_rand_state = (uint32_t)(seed);
+	(void)espeak_rand(0, 1); // Dummy flush a generator
+}
 

src/libespeak-ng/common.h

 extern ESPEAK_NG_API int GetFileLength(const char *filename);
 extern ESPEAK_NG_API void strncpy0(char *to, const char *from, int size);
 
+void espeak_srand(long seed);
+long espeak_rand(long min, long max);
+
 int IsAlpha(unsigned int c);
 int IsBracket(int c);
 int IsDigit(unsigned int c);

src/libespeak-ng/klatt.c

 #include <espeak-ng/speak_lib.h>
 
 #include "klatt.h"
+#include "common.h"      // for espeak_rand
 #include "synthesize.h"  // for frame_t, WGEN_DATA, STEPSIZE, N_KLATTP, echo...
 #include "voice.h"       // for voice_t, N_PEAKS
 #ifdef INCLUDE_SPEECHPLAYER
 static int nsamples;
 static int sample_count;
 
-#ifdef _MSC_VER
-#define getrandom(min, max) ((rand()%(int)(((max)+1)-(min)))+(min))
-#else
-#define getrandom(min, max) ((rand()%(long)(((max)+1)-(min)))+(min))
-#endif
+#define getrandom(min, max) espeak_rand((min), (max))
 
 // function prototypes for functions private to this file
 

src/libespeak-ng/speech.c

 	option_phonemes = 0;
 	option_phoneme_events = 0;
 
+	// Seed random generator
+	espeak_srand(time(NULL));
+
 	return ENS_OK;
 }
 

src/libespeak-ng/wavegen.c

 #include <espeak-ng/speak_lib.h>
 
 #include "wavegen.h"
+#include "common.h"                   // for espeak_rand
 #include "synthesize.h"               // for WGEN_DATA, RESONATOR, frame_t
 #include "mbrola.h"                  // for MbrolaFill, MbrolaReset, mbrola...
 
 	int ix;
 
 	// use two random numbers, for alternate formants
-	noise = (rand() & 0x3fff) - 0x2000;
+	noise = espeak_rand(-0x2000, 0x1fff);
 
 	for (ix = 1; ix < N_PEAKS; ix++) {
 		int amp;