JAVA-1165: Also backing out the test
JAVA-1167: Changed save and insert such that they check for the existence of the _id key rather than comparing it to null.  This lets you insert a document with _id of null (of course, you can't do that more than once per collection).
JAVA-1178: Remove special handling of jnote/wnote for pre-2.6 servers.
JAVA-1171:  Allowing query documents to exceed the maximum document size by 16K, so that, for example, the findAndModify command can be used to upsert a 16M document.  Without this headroom, the additional space taken by the surrounding command document would push it over 16M, and the driver would through an exception.  16K was chosen as the value because it matches the constant used in the server code base.