xstat() will never be implemented under Carbon. Fortunately it also doesn't appear to be used anywhere.
diff --git a/Mac/Modules/macmodule.c b/Mac/Modules/macmodule.c
index 9674ab7..b9a56ef 100644
--- a/Mac/Modules/macmodule.c
+++ b/Mac/Modules/macmodule.c
@@ -31,8 +31,8 @@
 #include <string.h>
 #include <errno.h>
 
-#if !TARGET_API_MAC_CARBON_NOTYET
-/* XXXX Skip for Carbon, for now */
+#if !TARGET_API_MAC_CARBON
+/* Skip for Carbon */
 #include "macstat.h"
 #endif
 
@@ -51,7 +51,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #else /* USE_GUSI */
-#if !TARGET_API_MAC_CARBON_NOTYET
+#if !TARGET_API_MAC_CARBON
 #define stat macstat
 #endif
 #endif /* USE_GUSI */
@@ -499,7 +499,7 @@
 }
 #endif /* WEHAVE_FSTAT */
 
-#if !TARGET_API_MAC_CARBON_NOTYET
+#if !TARGET_API_MAC_CARBON
 static PyObject *
 mac_xstat(self, args)
 	PyObject *self;
@@ -623,7 +623,7 @@
 	{"rename",	mac_rename},
 	{"rmdir",	mac_rmdir},
 	{"stat",	mac_stat},
-#if !TARGET_API_MAC_CARBON_NOTYET
+#if !TARGET_API_MAC_CARBON
 	{"xstat",	mac_xstat},
 #endif
 	{"sync",	mac_sync},