Import revision 49066 from v5-34-00 patch branch: Extent/correct the detection of renamed classes.   Avoid unitialized memory read during Fill-ing (read action use not yet ready ...)

This import has been previously inadvertently omitted.

git-svn-id: http://root.cern.ch/svn/root/branches/v5-34-00-patches@49066 27541ba8-7e3a-0410-8455-c3a389f83636
(cherry picked from v5-34-00-patch commit 05e082429c67603aeff9a001079cf31e6825b462)