Generate properly typed clone methods in productions

src/main/java/org/sablecc/sablecc/node/PAlt.java

src/main/java/org/sablecc/sablecc/node/PAltTransform.java

src/main/java/org/sablecc/sablecc/node/PAst.java

src/main/java/org/sablecc/sablecc/node/PAstAlt.java

src/main/java/org/sablecc/sablecc/node/PAstProd.java

src/main/java/org/sablecc/sablecc/node/PBasic.java

src/main/java/org/sablecc/sablecc/node/PBinOp.java

src/main/java/org/sablecc/sablecc/node/PChar.java

src/main/java/org/sablecc/sablecc/node/PConcat.java

src/main/java/org/sablecc/sablecc/node/PElem.java

src/main/java/org/sablecc/sablecc/node/PGrammar.java

src/main/java/org/sablecc/sablecc/node/PHelperDef.java

src/main/java/org/sablecc/sablecc/node/PHelpers.java

src/main/java/org/sablecc/sablecc/node/PIgnTokens.java

src/main/java/org/sablecc/sablecc/node/PListTerm.java

src/main/java/org/sablecc/sablecc/node/PProd.java

src/main/java/org/sablecc/sablecc/node/PProdName.java

src/main/java/org/sablecc/sablecc/node/PProductions.java

src/main/java/org/sablecc/sablecc/node/PRegExp.java

src/main/java/org/sablecc/sablecc/node/PSet.java