Split out MongoResultException into its own files.
Split out MongoCursorException into its own files.
Split out MongoCursorTimeoutException into its own files.
Split out MongoConnectionException into its own files.
Split out MongoException into its own files.
Split out MongoGridFSException into its own files.
Split out MongoGridFSException into its own files.
Removed ifdef as it is would allow for 5.1 support which we don't do anyway.
PHP-542: Split out exceptions into their own files.