Tried to reduce gap between both EWSGI proposals

Re-adapt the Spec-compliant solution (instead of Lib-compliant solution).
  Thus no more 100% deferred interface.
Rename EWSGI_RESPONSE into EWSGI_RESPONSE_BUFFER
Added in extra/response-as-result/  an copy/paste from the implementation of Paul's proposal (not up to date with Paul's spec). But this is mainly for information and tests.
Removed part of the ewsgi/specification interfaces ... to be able to test EWSGI compliant library against the pure specification (experimental).
Renamed most of the GW_... into EWSGI_...

library/server/ewsgi/src/application/ewsgi_agent_application.e

@@ -0,0 +1,48 @@
+note
+	description: "Summary description for {EWSGI_AGENT_APPLICATION}."
+	author: ""
+	date: "$Date$"
+	revision: "$Revision$"
+
+class
+	EWSGI_AGENT_APPLICATION
+
+inherit
+	EWSGI_APPLICATION
+
+create
+	make
+
+feature {NONE} -- Implementation
+
+	make (a_callback: like callback)
+			-- Initialize `Current'.
+		do
+			callback := a_callback
+		end
+
+feature {NONE} -- Implementation
+
+	callback: PROCEDURE [ANY, TUPLE [req: like new_request; res: like new_response]]
+			-- Procedure called on `execute'
+
+	execute (req: like new_request; res: like new_response)
+			-- Execute the request
+		do
+			callback.call ([req, res])
+		end
+
+invariant
+	callback_attached: callback /= Void
+
+note
+	copyright: "2011-2011, Eiffel Software and others"
+	license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)"
+	source: "[
+			Eiffel Software
+			5949 Hollister Ave., Goleta, CA 93117 USA
+			Telephone 805-685-1006, Fax 805-685-6869
+			Website http://www.eiffel.com
+			Customer support http://support.eiffel.com
+		]"
+end