extract method: add default modifier when extracted into interface (java 8 only)

java/java-tests/testData/refactoring/extractMethod/Method2Interface_after.java

@@ -0,0 +1,9 @@
+interface I {
+    default void foo () {
+        newMethod();
+    }
+
+    private default void newMethod() {
+        System.out.println("hello");
+    }
+}