Mutable case classes via vars in body

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

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

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

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

...ssion/verification/xlang/valid/ObjectParamMutation2.scala

...ssion/verification/xlang/valid/ObjectParamMutation3.scala

...ssion/verification/xlang/valid/ObjectParamMutation4.scala

...ssion/verification/xlang/valid/ObjectParamMutation5.scala

...ssion/verification/xlang/valid/ObjectParamMutation6.scala

...ssion/verification/xlang/valid/ObjectParamMutation7.scala

testcases/verification/xlang/FunctionCaching.scala