Converted code to void-safety and use better Eiffel feature naming.

Changed feature names to match Eiffel naming conventions.
Updated to use WSF_PAGE_RESPONSE which compute among other the Content-Length http header.
in Eiffel, we use "verb" for procedure .. and name for function/attribute
so when I read `get_error_msg' .. I expect it to be a procedure that assign attribute `error_msg'.

here in Eiffel style, we simply have "error_msg" .. or even "error_message" which is more readable.