include ogre without OGRE prefix

This is necessary to find Ogre files in the right place with
compatibility between Ogre < 1.9 and Ogre >= 1.9.

This is also necessary when 2 versions of Ogre are installed on the
build machine.
Add Ogre-1.10 compatibility

This allows rviz to compile (and work) against Ogre 1.10 (currently
the latest version of ogre).

It also still works with earlier versions of Ogre (tested with Ogre
1.7.4 as installed via debs on Ubuntu 12.04).