Termination checker fixes for new DefOps and theory encoders

src/main/scala/leon/purescala/DefOps.scala

src/main/scala/leon/solvers/cvc4/CVC4UnrollingSolver.scala

src/main/scala/leon/solvers/smtlib/SMTLIBCVC4Solver.scala

src/main/scala/leon/solvers/smtlib/SMTLIBSolver.scala

src/main/scala/leon/solvers/smtlib/SMTLIBZ3Solver.scala

src/main/scala/leon/solvers/theories/BagEncoder.scala

src/main/scala/leon/solvers/theories/StringEncoder.scala

src/main/scala/leon/solvers/theories/TheoryEncoder.scala

src/main/scala/leon/solvers/unrolling/UnrollingSolver.scala

src/main/scala/leon/solvers/z3/FairZ3Solver.scala

src/main/scala/leon/solvers/z3/Z3UnrollingSolver.scala

src/main/scala/leon/termination/ChainProcessor.scala

src/main/scala/leon/termination/Processor.scala