Added is_available on HTTP_CLIENT_SESSION mainly to check if libcurl is available.

library/network/http_client/src/http_client_session.e

@@ -120,6 +120,11 @@ feature -- Status report
 	is_debug: BOOLEAN
 			-- Produce debug output
 
+	is_available: BOOLEAN
+			-- Is interface usable?
+		deferred
+		end
+			
 feature -- Settings
 
 	timeout: INTEGER

library/network/http_client/src/spec/libcurl/libcurl_http_client_session.e

@@ -23,6 +23,14 @@ feature {NONE} -- Initialization
 			curl_easy.set_curl_function (create {LIBCURL_DEFAULT_FUNCTION}.make)
 		end
 
+feature -- Status report
+
+	is_available: BOOLEAN
+			-- Is interface usable?
+		do
+			Result := curl.is_dynamic_library_exists
+		end
+
 feature -- Basic operation
 
 	get (a_path: READABLE_STRING_8; ctx: detachable HTTP_CLIENT_REQUEST_CONTEXT): HTTP_CLIENT_RESPONSE