Implement termination checker

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

src/main/scala/leon/purescala/Trees.scala

src/main/scala/leon/termination/ChainBuilder.scala

src/main/scala/leon/termination/ChainComparator.scala

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

...in/scala/leon/termination/ComplexTerminationChecker.scala

src/main/scala/leon/termination/ComponentBuilder.scala

src/main/scala/leon/termination/ComponentProcessor.scala

src/main/scala/leon/termination/LoopProcessor.scala

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

src/main/scala/leon/termination/RecursionProcessor.scala

src/main/scala/leon/termination/RelationBuilder.scala

src/main/scala/leon/termination/RelationComparator.scala

src/main/scala/leon/termination/RelationProcessor.scala

src/main/scala/leon/termination/SCC.scala

...ain/scala/leon/termination/SimpleTerminationChecker.scala

src/main/scala/leon/termination/StructuralSize.scala

src/main/scala/leon/termination/TerminationChecker.scala

src/main/scala/leon/termination/TerminationPhase.scala

src/main/scala/leon/termination/TerminationReport.scala