engine: gameui: add GetNativeObject to extended menu API

engine/client/cl_gameui.c

@@ -1220,6 +1220,7 @@ static ui_extendedfuncs_t gExtendedfuncs =
 	pfnParseFileSafe,
 	NET_AdrToString,
 	NET_CompareAdrSort,
+	Sys_GetNativeObject,
 };
 
 void UI_UnloadProgs( void )

engine/menu_int.h

@@ -215,6 +215,7 @@ typedef struct ui_extendedfuncs_s {
 	// network address funcs
 	const char *(*pfnAdrToString)( const struct netadr_s a );
 	int (*pfnCompareAdr)( const void *a, const void *b ); // netadr_t
+	void *(*pfnGetNativeObject)( const char *name );
 } ui_extendedfuncs_t;
 
 // deprecated export from old engine