Made class static a member of PFCheckHitPattern

Had to make a static std::map to be a member data of PFCheckHitPattern
to fix a crash in the threaded framework.
Merge pull request #3652 from Dr15Jones/makeStaticAMemberOfPFCheckHitPattern

Reco -- Made class static a member of PFCheckHitPattern
Merge remote branch 'origin/CMSSW_7_1_X' into CMSSW_7_0_X