update javaparser to 2.4.0

[sebastiankirsch]

To keep changes required for Java9 small, javaparser should be updated from 2.3.0 to 2.4.0.

Changes are those: javaparser/javaparser@924683c...9d87049

There are new types that may be relevant for the custom visitors:

• java/com/github/javaparser/ast/TypeArguments
• java/com/github/javaparser/ast/type/IntersectionType
• java/com/github/javaparser/ast/type/UnionType
• java/com/github/javaparser/ast/type/ReferenceTypeWithAnnotations
• java/com/github/javaparser/ast/type/ClassOrInterfaceTypeWithAnnotations

This may be adapted/helpful as well:

• ClassOrInterfaceType.getTypeArgs() now offers isUsingDiamondOperator()
• TryStatement.type
• CastExpression.st, CastExpression.typeOfMultiCast
• ImportDeclaration.isEmptyImportDeclaration()
• PackageDeclaration.getPackageName()