Output number of files merger in hadd -v1:

$ hadd -v 1 -f output.root input1.root input2.root 
Target file: output.root
Merged 2 input files.


git-svn-id: http://root.cern.ch/svn/root/trunk@41442 27541ba8-7e3a-0410-8455-c3a389f83636