Generic finite element implementations rely on undefined behaviour

All 'generic' finite element implementations, i.e., those building up on the infrastructure in dune/localfunctions/utility/ make heavy use of reinterpret_cast breaking strict aliasing rules. As a consequence evaluation of the basis functions leads to undefined behaviour.

For those not aware of strict aliasing errors: A typical manifestation of this is, that optimized code may silently compute wrong numbers in special cases because the compiler makes wrong assumptions on when to sync register values with memory.