8022658: Revisit FunctionalInterface on some core libs types

Reviewed-by: briangoetz, mduigou, mr

src/share/classes/java/io/Closeable.java

@@ -34,7 +34,6 @@ import java.io.IOException;
  *
  * @since 1.5
  */
-@FunctionalInterface
 public interface Closeable extends AutoCloseable {
 
     /**

src/share/classes/java/io/Flushable.java

@@ -34,7 +34,6 @@ import java.io.IOException;
  *
  * @since 1.5
  */
-@FunctionalInterface
 public interface Flushable {
 
     /**

src/share/classes/java/lang/AutoCloseable.java

@@ -48,7 +48,6 @@ package java.lang;
  * @author Josh Bloch
  * @since 1.7
  */
-@FunctionalInterface
 public interface AutoCloseable {
     /**
      * Closes this resource, relinquishing any underlying resources.

src/share/classes/java/lang/Comparable.java

@@ -93,7 +93,6 @@ import java.util.*;
  * @see java.util.Comparator
  * @since 1.2
  */
-@FunctionalInterface
 public interface Comparable<T> {
     /**
      * Compares this object with the specified object for order.  Returns a

src/share/classes/java/lang/Iterable.java

@@ -42,7 +42,6 @@ import java.util.function.Consumer;
  * @since 1.5
  * @jls 14.14.2 The enhanced for statement
  */
-@FunctionalInterface
 public interface Iterable<T> {
     /**
      * Returns an iterator over elements of type {@code T}.

src/share/classes/java/lang/Readable.java

@@ -34,7 +34,6 @@ import java.io.IOException;
  *
  * @since 1.5
  */
-@FunctionalInterface
 public interface Readable {
 
     /**