Originally by Dan Eicher, with my own fixes and adjustments (see patch page for details).
For details there are unit tests and api example usage.
doc/python_api/sphinx-in-tmp/menu_id.png
with Standard Notation
from Andrew Hale
Scripts which access matrix row/columns directly and scripts that create new matrices with elements defined will need updating.
For more info see...
* Guide for updating scripts
http://wiki.blender.org/index.php/User:TrumanBlending/Matrix_Indexing
* Discussion thread
http://markmail.org/message/4bpqpxkcvq4wjyfu