Martin; I've added calls like:
	BIF_TransformSetUndo("Add Duplicate");
In advance of calling transform itself, to indicate that this is the
string name to be used for Undo, and also has to be done on ESC.
To make that possible I had to add a memset() to zero the global struct
TransInfo. Nicely done with if(Trans.mode==TRANS_INIT)
Not sure how this relates to setting constraints in advance... I always
found it tricky to work a non-initalized global struct. :)