Add faster processing of btCompoundShape versus btCompoundShape, using a dedicated btCompoundCompoundCollisionAlgorithm,
with hash pair caching and tandem tree traversal. It should be much faster, when using many child shapes for both compounds.
Fix iOS compilation, added header.

git-svn-id: http://bullet.googlecode.com/svn@2661 08e121b0-ae19-0410-a57b-3be3395fd4fd