[osg-submissions] API configurations in a seperate Config include file

[Robert Osfield]

Hi J-S,

I am just doing an out of source build right now, and my first attempt
didn't succeed as the in source OpenSceneGraph/CMakeCache.txt was
still hanging around - I didn't get any errors though, it just didn't
generate an out of source build system.  Once I removed the offending
CMakeCache.txt running ccmake worked just fine.

CMake on my system is creating an include/OpenThreads/Config and
include/osg/Config local to the out of source build.

I wonder if your OpenSceneGraph/CMakeLists.txt has been modified
locally so that you aren't getting the SVN version.

Robert.