Bug#729289: transition: openscenegraph

[Alberto Luaces <aluaces@udc.es>]

Some additional notes:

1. Upstream's trunk (3.3.1) has currently a soname named "111".  From
the logs, it is just a version number bump, but it would make sense to
make sure that the ABI is not broken again.  Several weeks ago I used
abi-compliance-checker on OSG, but it failed to finish the analysis.

2. The transition page
(https://release.debian.org/transitions/html/osg.html) is titled
"libopenscenegraph100", but actually it deals with the "80" to "99"
transition.