Add const to constexpr non-static member function in SiPixelCluster.h

[davidlt]

In C++14 rule 'constexpr implies const' for non-static member functions is no more.
Explicitly add 'const' modifier to keep behavior identical between C++11 and C++14.

Signed-off-by: David Abdurachmanov David.Abdurachmanov@cern.ch

[cmsbuild]

A new Pull Request was created by @davidlt for CMSSW_7_0_X.

Add const to constexpr non-static member function in SiPixelCluster.h

It involves the following packages:

DataFormats/SiPixelCluster

@nclopezo, @cmsbuild, @thspeer, @slava77 can you please review it and eventually sign? Thanks.
You can sign-off by replying to this message having '+1' in the first line of your reply.
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@ktf you are the release manager for this.

[cmsbuild]

+1
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/1403/summary.html

[thspeer]

+1
Tested 04f8ad0 in CMSSW_7_0_X_2013-11-19-0200-1520
No difference in reco as expected, based on RelMon and reco script

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next IBs unless changes or unless it breaks tests. @ktf can you please take care of it?