CMSSW_9_3_15_patch1

Changes since CMSSW_9_3_15:

compare to previous

1. 26906 from @Andrej-CMS: Herwig7 fix seg fault93 x generators pdmv upgrade created: 2019-05-23 15:12:16 merged: 2019-05-28 16:39:28

2. 26881 from @intrepid42: Additional Photos options (9_3_X) generators created: 2019-05-22 09:32:39 merged: 2019-05-28 16:43:58

CMSDIST Changes between Tags REL/CMSSW_9_3_15/slc6_amd64_gcc630 and REL/CMSSW_9_3_15_patch1/slc6_amd64_gcc630:

compare to previous