More changes to support stainless

src/main/scala/inox/Program.scala

src/main/scala/inox/ast/DSL.scala

src/main/scala/inox/ast/Definitions.scala

src/main/scala/inox/ast/Expressions.scala

src/main/scala/inox/ast/Extractors.scala

src/main/scala/inox/ast/Printers.scala

src/main/scala/inox/ast/SimpleSymbols.scala

src/main/scala/inox/ast/Trees.scala

src/main/scala/inox/ast/TypeOps.scala

src/main/scala/inox/datagen/SolverDataGen.scala

src/main/scala/inox/evaluators/RecursiveEvaluator.scala

src/main/scala/inox/solvers/smtlib/SMTLIBTarget.scala

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

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

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

src/main/scala/inox/solvers/z3/AbstractZ3Solver.scala

src/test/scala/inox/evaluators/EvaluatorSuite.scala