Replace uses of legacy collections (Vector, Hashtable)

src/main/java/org/sablecc/sablecc/CharSet.java

src/main/java/org/sablecc/sablecc/DFA.java

src/main/java/org/sablecc/sablecc/GenLexer.java

src/main/java/org/sablecc/sablecc/GenParser.java

...org/sablecc/sablecc/GenerateAlternativeCodeForParser.java

src/main/java/org/sablecc/sablecc/Grammar.java

src/main/java/org/sablecc/sablecc/LR0Collection.java

src/main/java/org/sablecc/sablecc/LR0ItemSet.java

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

src/main/java/org/sablecc/sablecc/LR1ItemSet.java

src/main/java/org/sablecc/sablecc/Production.java

src/main/java/org/sablecc/sablecc/SableCC.java

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

src/main/java/org/sablecc/sablecc/SymbolSet.java