Thread safety fixes for TCint

-use thread_local for statics which are being used as return values
-use C++11 initializers to allow static containers to be const
-add lock to protect fgSetOfSpecials
Make function static return values thread_safe

Funciton level statics which are being used as return values from
the function are changed to thread_local. This is needed to avoid
multiple threads changing the values while they are being used.
Added missing locks when calling gCint

Added calls to the gCINTMutex lock when calling gCint methods. These
are needed to avoid problems while concurrently using TFormula.
Merge pull request #24 from Dr15Jones/anotherFixForTFormula

Another fix to make TFormula thread-safe