The previous implementation constructs proxy URI in OptionHandler but
it cannot handle with the situation when user, password and proxy URI
is given various order. Now we just set rules: username set in
--*-proxy-user overrides username in --*-proxy option, no matter in
any order username, password and proxy URI are parsed. Likewise,
password set in --*--proxy-passwd overrides password in --*-proxy
option.
Tatsuhiro Tsujikawa