changes are backwards compatible (btBulletWorldImporter can load old .bullet files)
but not forwards compatible (constraints in new .bullet files are ignored/unrecognized by old Bullet SDK)
This commit is for Issue 734. Some more work needs to be done for btGImpactMeshShapeDoubleData and thus btStridingMeshInterfaceDoubleData and btMeshPartDoubleData
add compound shape support to BulletXmlWorldImporter and fix some compile issue under Debian (hopefully)
object picking change in the demos: create a ball-socket picking constraint when holding shift while mouse dragging, otherwise a fixed (6dof) constraint
add assert in constraint solver, when both objects have their inertia tensor rows set to zero
btPolyhedralContactClipping: add edge-edge contact point in findSeparatingAxis (similar to the default GJK case)
update AntTweakBar version in CDTestFramework
add btCompoundShape support in BulletXmlWorldImporter (this importer is still premature/work-in-progress)