Multithreading fixes

Misc multithreading fixes.

- FastJet fixes from Chris.
- TMVA fixes from Chris.
- Adaptations to get sherpa to compile.
    
This is the same set of changes valdiated by @slava77 between CMSSW_7_2_DEVEL_X_2014-05-29-1400 and CMSSW_7_2_X_2014-05-29-1400.
    
Summary from Slava:
    
> Results in CMSSW_7_2_DEVEL_X_2014-05-29-1400    and
> CMSSW_7_2_X_2014-05-29-1400
> look the same based on fwlite-based diffs and DQM comparisons.
> tests included the short matrix and some higher stat "extended tests"
> (dijet, ele/mu/pho guns and ttbar with PU).

Changes will start to be used from CMSSW_7_2_X_2014-06-03-1400.

@davidlange6 @Dr15Jones