Add a warning in presence of the conditions described here ROOT-6947

print a warning when a class is selected twice, for example with
its name and a typedef to it.
It does not make sense to select twice the same entity within the
same selection and genreflex helps the user to figure out that
the situation can be improved.
In some sense this is an extension of the mechanism of duplicates
detection with rootmaps.
Add TGeoBranchArray::SizeOfInstance
Fix previous commit in TF1::GetHistogram  for TF2 and TF3
Remove dummy title from TEnums

it consumes memory and leads to incorrect qualified names
Use the newly serialized tokens instead of hitting disk (ROOT-6942).
Use Module::getNamedValue() to check for existing symbols (ROOT-6909).
To be consistent with the other GetNxxx() methods, the new method GetNHists() has been renamed GetNhists (thanks Axel to notice).
Fix ROOT-6866
fix ROOT-6962: "bug with underscore"
Add missing initialization in TEnum's constructor
Fix re-computation of limits when merging HypoTestINverterResult's
When copying histogram with a specific directory stored, add also the copied one in the specific directory
(see http://root.cern.ch/phpBB3/viewtopic.php?f=3&t=19057 )