Fixed a use-after-free.

But this does introduce a memory leak, curtesy of two splits in parameter
parsing, and MONGO_METHOD3. This patch is for 1.4 *only*, I'll cook up a real
fix for master.
Merged pull request #498
Merge branch 'v1.4'
PHP-820: Get rid of a MONGO_METHOD3 in MongoCollection::save().

This also fixes the memory leak that PR-497. Even though PHP-820 is for 1.5,
perhaps we can merge it to v1.4 too instead of PR-497.
Merged pull request #499