From Brian and Philippe:

Reduce the memory used by a TTree in half.

Refactor the code reading and writing the TBasket data.
A single transient buffer holding the compressed data is 
now managed by TTree (and could be made thread local)
rather than having one per TBranch.


git-svn-id: http://root.cern.ch/svn/root/trunk@39642 27541ba8-7e3a-0410-8455-c3a389f83636