Clean up imports in non-generated code

src/main/java/org/sablecc/sablecc/AcceptStates.java

src/main/java/org/sablecc/sablecc/AddAstProductions.java

.../sablecc/AddEventualEmptyTransformationToProductions.java

.../org/sablecc/sablecc/AddProdTransformAndAltTransform.java

src/main/java/org/sablecc/sablecc/AltTransformAdapter.java

...ain/java/org/sablecc/sablecc/AlternativeElementTypes.java

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

src/main/java/org/sablecc/sablecc/ComputeCGNomenclature.java

src/main/java/org/sablecc/sablecc/ComputeInlining.java

...n/java/org/sablecc/sablecc/ComputeSimpleTermPosition.java

src/main/java/org/sablecc/sablecc/ConflictException.java

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

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

src/main/java/org/sablecc/sablecc/ConstructProdsMap.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