adding new method into InterpolatingProver, that returns an inductive sequence of interpolants directly from the underlying SMT-solver. There seems to be no difference (in verification-results) towards the current iterative approach, that uses the same proof for interpolating all sublists of formulas.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@13916 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c