More changed to accomodate stainless

src/main/scala/inox/ast/CallGraph.scala

src/main/scala/inox/ast/Constructors.scala

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

src/main/scala/inox/ast/ExprOps.scala

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

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