Additional thread safety fixes

These changes fix a periodic crash which was occuring while running the threaded version of CMS' reconstruction code. The problem was a bad interaction between rebinning of a TProfile while being filled and the cloning of a TFormula. The problem stemmed from insufficient locking of cint data structures.
As part of the change, additional error reporting for the case where cloning fails was added. These reports were extremely useful in tracking down the problem and may prove useful in the future if a similar problem surfaces again.