It turns out that some calls return AEDesc records that are "borrowed",
the AEDesc data shouldn't be disposed when the Python object is.
Added a C call AEDesc_NewBorrowed() to create these objects and a Python
method old=AEDesc.AutoDispose(onoff) to change auto-dispose state.
diff --git a/Python/mactoolboxglue.c b/Python/mactoolboxglue.c
index 3dfd699..16ed3b5 100644
--- a/Python/mactoolboxglue.c
+++ b/Python/mactoolboxglue.c
@@ -534,6 +534,7 @@
GLUE_CONVERT(FSRef, PyMac_GetFSRef, "macfs")
GLUE_NEW(AppleEvent *, AEDesc_New, "Carbon.AE") /* XXXX Why by address? */
+GLUE_NEW(AppleEvent *, AEDesc_NewBorrowed, "Carbon.AE")
GLUE_CONVERT(AppleEvent, AEDesc_Convert, "Carbon.AE")
GLUE_NEW(Component, CmpObj_New, "Carbon.Cm")