Made _bypass field protected.

This is needed because the _content field is also protected, and subclasses
may need to know if the generator is in bypass mode (and therefore access
the _content buffer directly).

jetty-http/src/main/java/org/eclipse/jetty/http/HttpGenerator.java

@@ -105,7 +105,7 @@ public class HttpGenerator extends AbstractGenerator
     }
 
     // data
-    private boolean _bypass = false; // True if _content buffer can be written directly to endp and bypass the content buffer
+    protected boolean _bypass = false; // True if _content buffer can be written directly to endp and bypass the content buffer
     private boolean _needCRLF = false;
     private boolean _needEOC = false;
     private boolean _bufferChunked = false;