LArWheelCalculator: cleanup parameterization code

Instead of using a mutex in fill_sincos_parameterization, make the code thread-safe by profiting from the local static initialization guarantees of C++11.

The parameterizations for the inner/outer wheel are calculated (and cached) in two separate functions on first invocation. For each instance of LArWheelCalculator, the values then only need to be copied into the instance members. This also avoids the code duplication for the cached/non-cached case.

Other changes:

• change from C arrays to std::array
• fix the size of the arrays to LARWC_SINCOS_POLY+1=6 (the size was still set to 7, presumably from earlier versions)
• enable thread-checker