8059976: Convert JavacFileManager to use java.nio.file internally
Reviewed-by: jlahoda

8061876: replace java.io.File with java.nio.file.Path (again)
Reviewed-by: ksrini, jlahoda

8061723: 8060056 breaks tests on Windows
Reviewed-by: darcy

8060056: replace java.io.File with java.nio.file.Path
Reviewed-by: ksrini, jlahoda

8027310: Annotation Processor crashes with NPE
Summary: JCAnnotation.attribute is null when annotation type is unavailable
Reviewed-by: jjg, jfranck