Merge branch 'topic/mutable-classes'

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

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

src/main/scala/leon/purescala/DefOps.scala

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

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

src/main/scala/leon/purescala/PrettyPrinter.scala

src/main/scala/leon/purescala/Types.scala

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

src/main/scala/leon/xlang/AntiAliasingPhase.scala

src/main/scala/leon/xlang/Expressions.scala

...gression/verification/xlang/invalid/FunctionCaching.scala

...regression/verification/xlang/valid/FunctionCaching.scala

...n/verification/xlang/valid/ObjectHierarchyMutation1.scala

...n/verification/xlang/valid/ObjectHierarchyMutation2.scala

...n/verification/xlang/valid/ObjectHierarchyMutation3.scala

...n/verification/xlang/valid/ObjectHierarchyMutation4.scala

...n/verification/xlang/valid/ObjectHierarchyMutation5.scala

...n/verification/xlang/valid/ObjectHierarchyMutation6.scala

...n/verification/xlang/valid/ObjectHierarchyMutation7.scala

...ssion/verification/xlang/valid/ObjectParamMutation1.scala