Fix remaining javac warnings

src/main/java/org/sablecc/sablecc/ConstructNFA.java

...a/org/sablecc/sablecc/ConstructParserGenerationDatas.java

src/main/java/org/sablecc/sablecc/IntSet.java

src/main/java/org/sablecc/sablecc/LR1Collection.java

src/main/java/org/sablecc/sablecc/Symbol.java