Simplify imports, no need to process them whenever we update functions

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/FunctionMapping.scala

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

src/main/scala/leon/utils/InliningPhase.scala

src/test/scala/leon/test/purescala/DefOpsSuite.scala