Merge pull request #1 from ashleyfrieze/ashleyfrieze-autocloseable

Make the `StreamGenerator` an `AutoCloseable`

Author: ashleyfrieze

pg/src/main/java/org/bouncycastle/openpgp/StreamGenerator.java

@@ -4,13 +4,14 @@
 
 /**
  * Callback interface for generators that produce a stream to be informed when the stream has been
- * closed by the client.
+ * closed by the client. Complies with Java's own {@link AutoCloseable} interface
  */
-interface StreamGenerator
+interface StreamGenerator extends AutoCloseable
 {
     /**
      * Signal that the stream has been closed.
      */
+    @Override
     void close()
         throws IOException;
 }