Fixed dead() — something must have changed between the write and rebase.
Added an extra test case especially for ->dead().
Merged pull request #579
PHP-861: Added the MongoCursor::maxTimeMS() method.
Moved Hannes' duplicate key checking to mongo_cursor_throw() to merge with the timeouts.
Fixed comments as per review:

- Test filename
- prototype description
- variable name l -> time_ms
- error code check ordering
I hate this stupid 32bit nonsense.
Merged pull request #569