Fix a problem in FillN with the histograms with automatic binning (TH1, TH2 and Profile)
Fix previous commit in renaming the data member
Revert commit 14280dac4a88b279a014cb4b17afa920b2787e3c.
Copied histogram will have fDirectory =  gDirectory or zero depending on TH1::AddDirectoryStatus().
Document this in Th1::SetDirectory and TH1::Copy