* HttpClientChannel.cs: Changed text for user-agent header (removed references

	* HttpClientChannel.cs: Changed text for user-agent header (removed references
	  to MS.NET).
	  Removed try/catch from AsyncProcessRequest. If there is an exception it must
	  flow to the caller.
	  in AsyncRequestHandler, improved management of exceptions. HttpWebRequest
	  throws an exception if the result code is 400, 500. Is is not a communication
	  error, but an application or server error. The content of the body must be
	  deserialized like in normal responses.
	  In CreateWebRequest, if the stream being sent is a MemoryStream, use a more
	  efficient way of writing the content.
	  In SendAndRecieve, same as in AsyncRequestHandler. Also moved some code to a
	  new method named ReceiveResponse, so it can be reused from AsyncRequestHandler.
	* HttpHelper.cs: Removed some debugging code that is not needed.
	* HttpServer.cs: Improved formatting of some code.
	  In CheckRequest method, send a 100-continue response if the request has
	  the header: expect:100-continue.
	  Method SendResponse: the remoting formatter may include the result code and
	  reason phrase to use in the transport headers. Used them if provided.
	* HttpServerChannel.cs: Use ThreadPool to create the thread that will answer
	  a request.

svn path=/trunk/mcs/; revision=17515