added overloaded method to the DefaultChannelPipeline in order to avoid unnecessary allocation

Motivation :

Avoid unnecessary array allocation when using the function with varargs in the DefaultChannelPipeline class.

Modifications :

Added addLast and addFirst overloaded methods with 1 handler instead of varargs.

Result :

No array allocation when using simple construction like pipeline.addLast(new Handler());

transport/src/main/java/io/netty/channel/DefaultChannelPipeline.java

@@ -354,6 +354,10 @@ public class DefaultChannelPipeline implements ChannelPipeline {
         ctx.next = newCtx;
     }
 
+    public final ChannelPipeline addFirst(ChannelHandler handler) {
+        return addFirst(null, handler);
+    }
+
     @Override
     public final ChannelPipeline addFirst(ChannelHandler... handlers) {
         return addFirst(null, handlers);
@@ -383,6 +387,10 @@ public class DefaultChannelPipeline implements ChannelPipeline {
         return this;
     }
 
+    public final ChannelPipeline addLast(ChannelHandler handler) {
+        return addLast(null, handler);
+    }
+
     @Override
     public final ChannelPipeline addLast(ChannelHandler... handlers) {
         return addLast(null, handlers);