added proof reconstructon for Z3,
added certificates for simpler re-checking of proofs (no need to invoke external solvers),
added examples and certificates for all examples,
removed Unsynchronized.ref (in smt_normalize.ML)

(benchmark Isabelle

:extrasorts ( T1)

:extrapreds (

  (up_1)

  (up_2)

 )

:assumption (and (or up_1 up_2) (not up_1))

:assumption (not up_2)

:formula true

)