Support the fraction of (Oracle) MySQL Fabric that is supported by the most recent Connector/C

The most recent labs release of Connector/C (6.2.0) has partial support for Oracle MySQL's Fabric. This patch exposes that functionality in libmysql to Perl via a set of DBI/tie attributes and a connect-time %attr entry. It's properly #ifdef'd out in case the version of libmysql is not high enough to include support for Fabric.

Alas, so far no documentation. Tests are icky since expecting a fully working Fabric test setup is asking a bit much of users.

See also: https://blogs.oracle.com/mysqlconnectors-C/entry/using_fabric_with_connector_c
Labs release 6.2.0: http://downloads.mysql.com/snapshots/pb/mysql-connector-c-6.2.0-labs/mysql-connector-c-6.2.0-labs-src.tar.gz

(Pair programmed with Eric Herman. Eric says hi!)