Added let bindings in leon paths

src/main/scala/leon/codegen/CodeGeneration.scala

src/main/scala/leon/codegen/runtime/Monitor.scala

src/main/scala/leon/evaluators/RecursiveEvaluator.scala

src/main/scala/leon/evaluators/StreamEvaluator.scala

src/main/scala/leon/grammars/Grammars.scala

src/main/scala/leon/grammars/SafeRecursiveCalls.scala

src/main/scala/leon/laziness/ClosurePreAsserter.scala

src/main/scala/leon/purescala/Definitions.scala

src/main/scala/leon/purescala/ExprOps.scala

src/main/scala/leon/purescala/FunctionClosure.scala

src/main/scala/leon/purescala/Path.scala

src/main/scala/leon/purescala/Quantification.scala

src/main/scala/leon/purescala/SimplifierWithPaths.scala

src/main/scala/leon/purescala/TransformerWithPC.scala

src/main/scala/leon/repair/Repairman.scala

src/main/scala/leon/repair/rules/Focus.scala

src/main/scala/leon/solvers/sygus/SygusSolver.scala

...main/scala/leon/solvers/unrolling/TemplateGenerator.scala

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

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