8008267: Add @Supported annotation to com.sun.source types

Reviewed-by: jjg

langtools/src/share/classes/com/sun/source/tree/MethodTree.java

@@ -46,6 +46,7 @@ import javax.lang.model.element.Name;
  * @author Jonathan Gibbons
  * @since 1.6
  */
+@jdk.Supported
 public interface MethodTree extends Tree {
     ModifiersTree getModifiers();
     Name getName();