code cleanup: static uri_callback

src/libespeak-ng/speech.c

 static espeak_ng_STATUS err = ENS_OK;
 
 static t_espeak_callback *synth_callback = NULL;
-int (*uri_callback)(int, const char *, const char *) = NULL;
 int (*phoneme_callback)(const char *) = NULL;
 
 char path_home[N_PATH_HOME]; // this is the espeak-ng-data directory
 #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;

src/libespeak-ng/ssml.c

 	{ NULL, 0 }
 };
 
+static int (*uri_callback)(int, const char *, const char *) = NULL;
+
 static int attrcmp(const wchar_t *string1, const char *string2)
 {
 	int ix;
 	return 0;
 }
 
+#pragma GCC visibility push(default)
+ESPEAK_API void espeak_SetUriCallback(int (*UriCallback)(int, const char *, const char *))
+{
+	uri_callback = UriCallback;
+}
+#pragma GCC visibility pop
+
 static const MNEM_TAB xml_entity_mnemonics[] = {
 	{ "gt",   '>' },
 	{ "lt",   0xe000 + '<' },   // private usage area, to avoid confusion with XML tag

src/libespeak-ng/translate.h

 extern espeak_ng_TEXT_DECODER *p_decoder;
 extern int dictionary_skipwords;
 
-extern int (*uri_callback)(int, const char *, const char *);
 extern int (*phoneme_callback)(const char *);
 
 #define LEADING_2_BITS 0xC0 // 0b11000000