new argument "adopt" to TBuffer ctor and to SetBuffer(). The default

value of the argument is kTRUE. When this value is kFALSE the buffer
passed will not be adopted by TBuffer and not deleted in the dtor
or in SetBuffer() when a new buffer is passed in. The default value
of adopt is backward compatible.


git-svn-id: http://root.cern.ch/svn/root/trunk@3334 27541ba8-7e3a-0410-8455-c3a389f83636