Commits:
http://github.com/jeremyselan/OpenColorIO/commit/f5a80ee9e46eab956de7d618abda866af81de0e7
http://github.com/jeremyselan/OpenColorIO/commit/9859c936bd4c17651ec2a4ae33fa23c6476fc6d2

These checkins expose additional build options on the command-line
(needed for custom facility install scripts).
* SOVERSION can now be exposed, and overridden, on the command-line (a
la openimageio)
* The python so can be built with, or without, the "lib" prefix.

This checkin does *not* change any build default values. Default
behavior should be identical.

-- Jeremy