Parsing for source level broken under JDK9 due to change in 1.X->X versioning by oracle.

src/core/lombok/javac/JavacAST.java

@@ -125,6 +125,8 @@ public class JavacAST extends AST<JavacAST, JavacNode, JCTree> {
 			String nm = Source.instance(context).name();
 			int underscoreIdx = nm.indexOf('_');
 			if (underscoreIdx > -1) return Integer.parseInt(nm.substring(underscoreIdx + 1));
+			// assume java9+
+			return Integer.parseInt(nm);
 		} catch (Exception ignore) {}
 		return 6;
 	}