o RooHistPdf

    - Fix plotSamplingHints() method that was broken
 o RooHistPdf

   - In importWorkspaceHook() apply more robust strategy to detect if existing RooDataHists
     in workspace really match to those in pdf: perform bin-by-bin content check instead
     of matching by name: if content is different from existing RooDataHist, clone and rename
     RooDataHist of pdf including pdf name in histogram name
 o RooHistPdf

   - Fix bug in lvalue conversion logic in plotSamplingHist