DataFormats/Histograms: rename `debug' macro to `METOEDMFORMAT_DEBUG'

The following is needed for ROOT6.

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>
Merge pull request #1998 from davidlt/DataFormats-Histograms-debug-to-METOEDMFORMAT_DEBUG

DataFormats/Histograms: rename `debug' macro to `METOEDMFORMAT_DEBUG'
Merge remote branch 'origin/CMSSW_7_0_X' into CMSSW_7_0_X