Upgrade OpenSceneGraph to 3.2.1

[Ralf Corsepius]

Hi,

I intend to upgrade OpenSceneGraph to 3.2.1 (Jul 4th) on rawhide.

This change will introduce SONAME bumps in OpenSceneGraph-provided 
libraries and thus is likely to introduce broken package dependencies.

I intend to take care about these and to launch rebuilds where necessary.

Depending on how well things work out, I am considering to also upgrade 
on f21, but it's too early to have a strong opinion on this.

Ralf