Improve FunDef signature

src/main/scala/leon/datagen/SolverDataGen.scala

src/main/scala/leon/frontends/scalac/CodeExtraction.scala

...scala/leon/invariant/engine/UnfoldingTemplateSolver.scala

src/main/scala/leon/invariant/structure/FunctionUtils.scala

src/main/scala/leon/invariant/util/Util.scala

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

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

src/main/scala/leon/purescala/MethodLifting.scala

src/main/scala/leon/purescala/RestoreMethods.scala

src/main/scala/leon/purescala/TypeOps.scala

src/main/scala/leon/solvers/isabelle/AdaptationPhase.scala

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

...main/scala/leon/solvers/templates/TemplateGenerator.scala

src/main/scala/leon/synthesis/rules/ADTInduction.scala

src/main/scala/leon/synthesis/rules/ADTLongInduction.scala

src/main/scala/leon/synthesis/rules/CEGISLike.scala

src/main/scala/leon/synthesis/rules/IntInduction.scala

...main/scala/leon/synthesis/rules/IntegerInequalities.scala

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

src/main/scala/leon/transformations/InstProgSimplifier.scala