Improved the libcurl implementation of http_client by adding HTTP_CLIENT_SESSION.is_debug: BOOLEAN

if True, this display verbose debug information in console
Implemented uploading of file for PUT and POST requests
Refactored LIBCURL_HTTP_CLIENT_REQUEST to free used pointer, and also ease extension of the class if needed.
Updated cURL library with addition of {CURL_EXTERNALS}.slist_free_all (..)

library/client/http_client/src/http_client_request.e

@@ -31,6 +31,14 @@ feature {NONE} -- Initialization
 
 	context: detachable HTTP_CLIENT_REQUEST_CONTEXT
 
+feature -- Status report
+
+	is_debug: BOOLEAN
+			-- Debug mode enabled?
+		do
+			Result := session.is_debug
+		end
+
 feature -- Access
 
 	request_method: READABLE_STRING_8