Remove the unused wave_test_get_write_buffer.

src/libespeak-ng/wave.c

 		wave_port_set_callback_is_output_enabled(cb);
 }
 
-void *wave_test_get_write_buffer()
-{
-	if (pulse_running)
-		return wave_pulse_test_get_write_buffer();
-	else
-		return wave_port_test_get_write_buffer();
-}
-
 int wave_get_remaining_time(uint32_t sample, uint32_t *time)
 {
 	if (pulse_running)
 #define wave_get_write_position wave_port_get_write_position
 #define wave_flush wave_port_flush
 #define wave_set_callback_is_output_enabled wave_port_set_callback_is_output_enabled
-#define wave_test_get_write_buffer wave_port_test_get_write_buffer
 #define wave_get_remaining_time wave_port_get_remaining_time
 
 #endif
 	return 0;
 }
 
-void *wave_test_get_write_buffer()
-{
-	return myWrite;
-}
-
 #else
 
 void *wave_open(int srate, const char *device)
 	(void)cb; // unused
 }
 
-extern void *wave_test_get_write_buffer()
-{
-	return NULL;
-}
-
 int wave_get_remaining_time(uint32_t sample, uint32_t *time)
 {
 	(void)sample; // unused

src/libespeak-ng/wave.h

 extern void clock_gettime2(struct timespec *ts);
 extern void add_time_in_ms(struct timespec *ts, int time_in_ms);
 
-// for tests
-extern void *wave_test_get_write_buffer();
-
 #ifdef __cplusplus
 }
 #endif

src/libespeak-ng/wave_pulse.c

 #define wave_get_write_position wave_pulse_get_write_position
 #define wave_flush wave_pulse_flush
 #define wave_set_callback_is_output_enabled wave_pulse_set_callback_is_output_enabled
-#define wave_test_get_write_buffer wave_pulse_test_get_write_buffer
 #define wave_get_remaining_time wave_pulse_get_remaining_time
 
 // check whether we can connect to PulseAudio
 	return 0;
 }
 
-void *wave_test_get_write_buffer()
-{
-	return NULL;
-}
-
 #endif

src/libespeak-ng/wave_sada.c

 	my_callback_is_output_enabled = cb;
 }
 
-// wave_test_get_write_buffer
-//
-// DESCRIPTION:
-//
-// Unnecessary and is used for debug output from
-// speak_lib.cpp:dispatch_audio.
-//
-// RETURNS:
-//
-// NULL
-//
-void *wave_test_get_write_buffer()
-{
-	return NULL;
-}
-
 // wave_get_read_position
 //
 // DESCRIPTION: