Move callback API implementations back to speech.c.

src/libespeak-ng/espeak_api.c

 	return espeak_ng_GetSampleRate();
 }
 
-ESPEAK_API void espeak_SetSynthCallback(t_espeak_callback *SynthCallback)
-{
-	synth_callback = SynthCallback;
-#ifdef USE_ASYNC
-	event_set_callback(synth_callback);
-#endif
-}
-
-ESPEAK_API void espeak_SetUriCallback(int (*UriCallback)(int, const char *, const char *))
-{
-	uri_callback = UriCallback;
-}
-
-ESPEAK_API void espeak_SetPhonemeCallback(int (*PhonemeCallback)(const char *))
-{
-	phoneme_callback = PhonemeCallback;
-}
-
 ESPEAK_API espeak_ERROR espeak_Synth(const void *text, size_t size,
                                      unsigned int position,
                                      espeak_POSITION_TYPE position_type,

src/libespeak-ng/speech.c

 
 #pragma GCC visibility push(default)
 
+ESPEAK_API void espeak_SetSynthCallback(t_espeak_callback *SynthCallback)
+{
+	synth_callback = SynthCallback;
+#ifdef USE_ASYNC
+	event_set_callback(synth_callback);
+#endif
+}
+
+ESPEAK_API void espeak_SetUriCallback(int (*UriCallback)(int, const char *, const char *))
+{
+	uri_callback = UriCallback;
+}
+
+ESPEAK_API void espeak_SetPhonemeCallback(int (*PhonemeCallback)(const char *))
+{
+	phoneme_callback = PhonemeCallback;
+}
+
 ESPEAK_NG_API espeak_ng_STATUS
 espeak_ng_Synthesize(const void *text, size_t size,
                      unsigned int position,