allow to build without any post processing steps:
* typo in ASSIMP_BUILD_DEBONE_PROCESS -> ASSIMP_BUILD_NO_DEBONE_PROCESS
* needs to include ProcessHelper.h itself
+ introduce aiScene::mPrivate. This is a potentially breaking API change. The new member is added at the end of the structure though, so serious regressions are not to be expected.
+ add a mPreprocessing parameter to all Export API calls. Allow exporters to specify further PP steps to be executed prior to handing control to them. The entire export API now operates on a copy of the scene that the user passed in.
- mass refactoring: all constructors of BaseProcess/BaseImporter inherited classes are public now and Importer will perhaps feel a bit sad after having loft all of its friends.
# fix const correctness in SceneCombiner
git-svn-id: https://assimp.svn.sourceforge.net/svnroot/assimp/trunk@1060 67173fc5-114c-0410-ac8e-9d2fd5bffc1f