Update VectorClass

1. Update VectorClass to latest version.

2. Add the missing instrset_detect.cpp file to the library. Should have been there before, as the header was being exported. Only worked because GaudiKernel happens to also export the same method (even though it shouldn't really as it uses it as an internal implementation detail, and does not export the associated header). In fact we where being very luck as the header and implementation where not even from the same release... This will be fixed once gaudi/Gaudi!392 (merged) is accepted which hides the Gaudi usage inside the Gaudi namespace at which point users will have to pick up the correct version from the VectorClassLib library.

3. Explicitly link LHCbMath against VectorClassLib to pick up instrset_detect() from there.

4. Update CPUDispatch.h with AVX512 enums.