Improvements in finding class methods

[wmtan]

Some improvements in finding class methods in the cut parser and expression parser:

1. Try first calling TClass::GetMethodWithPrototype(), which finds the best match function in the class or its base classes if the signature is correct.
2. Don't reject functions found in a base class from the result of TClass::GetMethodWithPrototype().
3. Cache the results, so this function is called at most once for any specific member function.
   Includes two other minor improvements in TypeWithDict.
   Please merge this request as soon as convenient.

[cmsbuild]

A new Pull Request was created by @wmtan for CMSSW_7_4_ROOT6_X.

Improvements in finding class methods

It involves the following packages:

CommonTools/Utils
FWCore/Utilities

@nclopezo, @cvuosalo, @monttj, @cmsbuild, @Dr15Jones, @slava77, @vadler, @ktf 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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