Fixed some tests due to server changes in 2.5.
Fixed some tests with the latests server changes.
The server started issuing a "code" field now for writeConcern failures.

This changed the code that we were showing from our default (4) to the new 64
(see:
https://github.com/mongodb/mongo/blob/master/src/mongo/base/error_codes.err)
More test fixes and allow < version checks too.
Fix PHP-426 test for mongod 2.5.x

Querying system.users is not reliable since the server API changes in 2.5.x. Instead, we can simply query a collection to test if the connection was successfully established.
Fix PHP-629 test for mongod 2.5.x

Use buildInfo command instead of evaluating "db.version()" JavaScript. On 2.5.x, users require explicit permission to evaluate JavaScript.

Use of the "timeout" option is irrelevant here, in light of bug00683.phpt and mongoclient-ctor-002.phpt.
Merge pull request #572