Better cookie handling

Some sites are sending cookies with expiration date far in the future. This causes trouble when LWPCookieJar is used to process cookies on 32bit system (or more precise system that uses 32bit time_t values).

Problem is well described here:
http://bugs.python.org/issue5537

This patch replaces LWPCookieJar by MozillaCookieJar that doesn't have such problem.