Added a formula evaluator to replace TFormula calls

[Dr15Jones]

Created a reco::FormulaEvaluator class which can parse a subset of
the TFormula expressions. The parsing and function evaluation are
done using stateless classes so are thread safe and extremely thread
efficient. The formula parser is shared by all reco::FormulaEvaluators
to save memory and since the parser is stateless it can efficiently
be called by multiple threads simultaneously.

This is a back port from CMSSW_7_6 of #11516

[cmsbuild]

A new Pull Request was created by @Dr15Jones (Chris Jones) for CMSSW_7_4_X.

Added a formula evaluator to replace TFormula calls

It involves the following packages:

CommonTools/Utils

@cmsbuild, @cvuosalo, @vadler, @monttj, @slava77 can you please review it and eventually sign? Thanks.
@makortel 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.

[cmsbuild]

+1
Tested at: 179d4e9
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-11554/8484/summary.html

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-11554/8484/summary.html

[slava77]

+1

for #11554 179d4e9

• the same (all new) code as in 62X no crossing frame #1516, no effect on running workflows
• jenkins tests pass

[davidlange6]

+1

[Dr15Jones]

This needs the bug fix applied to CMSSW_7_6. I'll try to back port at the airport.

[Dr15Jones]

There isn't a problem with this merge since the code isn't used in 7_4 yet.