Make cursor info() work on 32bit platforms.

We need to always force long as object for 32bit platforms when calling
->info(), otherwise we can not represent the cursor ID reliably.
Split test into 32bit and 64bit variant.
This test still used old MongoCursorCommand semantics.

Travis and Jenkins never ran this so didn't pick it up. Apparently, I hadn't
tested with 32bit either before.
Merged pull request #696