Update to 4.12:

4.12 Sun Jun 04 2010: - Balint Szilakszi <szbalint at cpan.org>

    - Fixed WWW::Curl::Form (patch contributed by Michael Ing).
    - Added CURLPROXY_* constants (patch by claes).
    - Added the const_string method to provide access to constants in a non-bareword way.
    - Fixed t/01basic.t test failure on older libcurl versions.

(wiz)