Add code for a ConstraintsState taking advantage of the ProverEnvironment stack.

Using this ConstraintsState is currently not working, as only one ProverEnvironment at a time can be created.



git-svn-id: https://svn.sosy-lab.org/software/cpachecker/branches/symbolic@15172 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c