Reintroduce BUrlResult and add BDataRequest

* BUrlResult is back, with ContentType and Length methods.
* BHttpResult subclasses it and use HTTP header fields to implement
those
* Introduce BDataRequest for "data" URIs. These embed the data inside
the URI, either as plaintext or base64 encoded.

headers/os/net/DataRequest.h

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2013 Haiku, Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Adrien Destugues, [email protected]
+ */
+
+
+#ifndef _B_DATA_REQUEST_H_
+#define _B_DATA_REQUEST_H_
+
+
+#include <UrlRequest.h>
+
+
+class BDataRequest: public BUrlRequest {
+public:
+							BDataRequest(const BUrl& url,
+								BUrlProtocolListener* listener = NULL,
+								BUrlContext* context = NULL);
+		const BUrlResult&	Result() const;
+private:
+		status_t			_ProtocolLoop();	
+private:
+		BUrlResult			fResult;
+};
+
+#endif