Improve exception handling and resource management in non-generated code

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

src/main/java/org/sablecc/sablecc/DisplayLicense.java

src/main/java/org/sablecc/sablecc/GenAlts.java

src/main/java/org/sablecc/sablecc/GenAnalyses.java

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

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

src/main/java/org/sablecc/sablecc/GenProds.java

src/main/java/org/sablecc/sablecc/GenTokens.java

src/main/java/org/sablecc/sablecc/GenUtils.java

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

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

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