refactors CtStatementList: removes the useless generic parameter <R>
refactors CtBlock: now extends CtStatementList

one can thus write:
for (CtStatement s : block) {
  l.add(s);
}
refactors CtCase: now extends CtStatementList

one can thus write:
for (CtStatement s : case) {
 l.add(s);
}