Use TClass::Destructor to properly handle the emulated class case
In ReadObject warns and return immediately after failed allocation
Fix TTreeFormula to prevent miscaculation in case like: http://root.cern.ch/phpBB3/viewtopic.php?t=18049.

Test was using the wrong boundary condition that resulted in the data branches
sometimes not being read (when using graphical cuts as the first part of the
expressions)