merged the opt/c changes back into the trunk (finally!)

svn: r5481

original commit: 4ad8fdadeaf56e8e373a947f6d2d0f451d959233

collects/mzlib/contract.ss

@@ -9,14 +9,10 @@
            "private/contract-basic-opters.ss")
   
   (provide 
-   ;; opt is not ready yet
-   #;(all-from "private/contract-opt.ss")
-   #;(all-from-except "private/contract-opt-guts.ss"
-                    make-opt-contract
-                    orig-ctc-prop
-                    orig-ctc-pred?
-                    orig-ctc-get)
-   (all-from "private/contract-ds.ss")
+   opt/c ;(all-from "private/contract-opt.ss")
+   (all-from-except "private/contract-ds.ss"
+                    lazy-depth-to-look)
+
    (all-from-except "private/contract-arrow.ss"
                     check-procedure)
    (all-from-except "private/contract-guts.ss"