Add missing include to XercesStrUtils.h

[Teemperor]

We use istringstream in this header, so we also need a include
to sstream.

[Teemperor]

Part of the work to solve the issue #15248

[cmsbuild]

A new Pull Request was created by @Teemperor (Raphael Isemann) for master.

It involves the following packages:

Utilities/Xerces

@cmsbuild, @smuzaffar, @Dr15Jones, @davidlange6 can you please review it and eventually sign? Thanks.
@Martin-Grunewald, @wddgit this is something you requested to watch as well.
@davidlange6 you are the release manager for this.

cms-bot commands are listed here

[Dr15Jones]

Please test

[Dr15Jones]

+1

[cmsbuild]

The tests are being triggered in jenkins.
https://cmssdt.cern.ch/jenkins/job/ib-any-integration/19923/console Started: 2017/05/17 13:44

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next master IBs after it passes the integration tests. This pull request requires discussion in the ORP meeting before it's merged. @davidlange6, @smuzaffar

[cmsbuild]

+1
Tested at: a320933
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-18791/19923/summary.html

[cmsbuild]

Comparison job queued.

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-18791/19923/summary.html

Comparison Summary:

• No significant changes to the logs found
• Reco comparison results: 1678 differences found in the comparisons
• DQMHistoTests: Total files compared: 24
• DQMHistoTests: Total histograms compared: 1833867
• DQMHistoTests: Total failures: 9382
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 1824305
• DQMHistoTests: Total skipped: 180
• DQMHistoTests: Total Missing objects: 0
• Checked 98 log files, 14 edm output root files, 24 DQM output files

[davidlange6]

+1