engine: add NET_AdrToString to menu extended API, upgrade mainui submodule

engine/menu_int.h

@@ -212,6 +212,8 @@ typedef struct ui_extendedfuncs_s {
 	double (*pfnDoubleTime)( void );
 
 	char *(*pfnParseFile)( char *data, char *buf, const int size, unsigned int flags, int *len );
+
+	const char	*(*pfnAdrToString)( const struct netadr_s a );
 } ui_extendedfuncs_t;
 
 // deprecated export from old engine