Add support for 5.6 connection attributes
allow unicode attributes (but convert them to the default character set)
Initial cut of the non-blocking interface, based on the Facebook MySQL 5.6.12
source tree's async client:

https://github.com/facebook/mysql-5.6

This interface is not yet final, but it is a starting point.
Clean up some excess print statements from a test case; also fix site.cfg
List ASYNC in the manifest
Fix issue with overzealous rename of a variable
Fix incorrect use of async state; use the true fd-based one instead
some helpful output from the example script
Add references to the string parameters while we are doing a connect; this prevents the underlying library from referencing invalid memory.
Merge fixes for mysqlclient-python