This commit updates the lifting and lowering done by Wasmtime to
validate that alignment is all correct. Previously alignment was ignored
because I wasn't sure how this would all work out.
To be extra safe I haven't actually modified any loads/stores and
they're all still unaligned. If this becomes a performance issue we can
investigate aligned loads and stores but otherwise I believe the
requisite locations have been guarded with traps and I've also added
debug asserts to catch possible future mistakes.
0b4448a423