Allow reading of files written with ROOT6 in ROOT5

[wmtan]

Bug fix: In ROOT6, the normalized names of three data types were changed from what they were in ROOT5. (unsigned) long long was changed to (U)Long64_t, and std::basic_string was changed to std::string. Because these names affect branch names, this creates an incompatibility between ROOT5 and ROOT6. The backward compatibility issue (reading ROOT5 files in ROOT6) was fixed a long time ago. However, at that time, I did not realize that ROOT provided the ability to read files written with ROOT6 in ROOT5. So, the compatibility fix was needed in the ROOT5 release as well.
Without this fix, ROOT/EDM files written in ROOT6 that contain a top level data item of any of the three affected types, OR of any type templated over these types (e.g. a vector of one of them) cannot be read in ROOT5.
Note: This fix is already in CMSSW_7_4_ROOT6_X.

[cmsbuild]

A new Pull Request was created by @wmtan for CMSSW_7_4_X.

Allow reading of files written with ROOT6 in ROOT5

It involves the following packages:

FWCore/Utilities

@cmsbuild, @Dr15Jones, @ktf, @nclopezo can you please review it and eventually sign? Thanks.
@Martin-Grunewald, @wddgit this is something you requested to watch as well.
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@Degano you are the release manager for this.
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[Dr15Jones]

Please test

[cmsbuild]

The tests are being triggered in jenkins.

[Dr15Jones]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_4_X IBs unless changes or unless it breaks tests. This pull request requires discussion in the ORP meeting before it's merged. @davidlange6, @Degano, @ktf, @smuzaffar

[cmsbuild]

+1
Tested at: 7357d55
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-7736/2605/summary.html

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_4_X IBs unless changes (tests are also fine). This pull request requires discussion in the ORP meeting before it's merged. @davidlange6, @Degano, @ktf, @smuzaffar

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-7736/2605/summary.html

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_4_X IBs unless changes (tests are also fine). This pull request requires discussion in the ORP meeting before it's merged. @davidlange6, @Degano, @ktf, @smuzaffar

[davidlange6]

+1