Simplify the Euler flux kernel.
Simplify the adiabatic wall BC kernel.
Improve the scalability of the OpenMP backend.
Remove some stray newlines.
Make the OpenMP::axnpby kernel parallel.
Ensure PYFR_ALIGN_BYTES is defined consistently.
Prefer arrays to pointers when declaring kernel argument types.
Simplify views in the advection-diffusion solver.

This saves some memory by exploiting the fact that a vector view
can also be used as a scalar view.
Merge branch 'feature/vectext' into develop.