Added missing @since 5.1 annotations
diff --git a/httpcore5/src/main/java/org/apache/hc/core5/http/impl/bootstrap/AsyncServer.java b/httpcore5/src/main/java/org/apache/hc/core5/http/impl/bootstrap/AsyncServer.java
index f64677d..fc46dea 100644
--- a/httpcore5/src/main/java/org/apache/hc/core5/http/impl/bootstrap/AsyncServer.java
+++ b/httpcore5/src/main/java/org/apache/hc/core5/http/impl/bootstrap/AsyncServer.java
@@ -86,6 +86,9 @@
         return ioReactor;
     }
 
+    /**
+     * @since 5.1
+     */
     public Future<ListenerEndpoint> listen(
             final SocketAddress address, final Object attachment, final FutureCallback<ListenerEndpoint> callback) {
         return ioReactor.listen(address, attachment, callback);
diff --git a/httpcore5/src/main/java/org/apache/hc/core5/http/impl/bootstrap/HttpAsyncServer.java b/httpcore5/src/main/java/org/apache/hc/core5/http/impl/bootstrap/HttpAsyncServer.java
index cb6ca43..32dde4c 100644
--- a/httpcore5/src/main/java/org/apache/hc/core5/http/impl/bootstrap/HttpAsyncServer.java
+++ b/httpcore5/src/main/java/org/apache/hc/core5/http/impl/bootstrap/HttpAsyncServer.java
@@ -83,6 +83,9 @@
         this(eventHandlerFactory, ioReactorConfig, ioSessionDecorator, exceptionCallback, sessionListener, null);
     }
 
+    /**
+     * @since 5.1
+     */
     public Future<ListenerEndpoint> listen(
             final SocketAddress address,
             final URIScheme scheme,
@@ -97,6 +100,9 @@
         return super.listen(address, parameters, callback);
     }
 
+    /**
+     * @since 5.1
+     */
     public Future<ListenerEndpoint> listen(
             final SocketAddress address,
             final URIScheme scheme,
@@ -104,6 +110,9 @@
         return listen(address, scheme, null, callback);
     }
 
+    /**
+     * @since 5.1
+     */
     public Future<ListenerEndpoint> listen(final SocketAddress address, final URIScheme scheme) {
         return listen(address, scheme, null, null);
     }