Previously, the assumption was made that ilmbase and openexr were installed in a common directory and hence the header files and libs were both found in that common directory. That is not consistent with other libs and this submission makes it consistent and therefore the OSG configures out of the box. I made this work for ilmbase-2.1.0.tar.gz / openexr-2.1.0.tar.gz and ilmbase-2.2.0.tar.gz / openexr-2.2.0.tar.gz
