Fixes

- NumPy letter code mismatch on some arch
- Revive inspect_types()
- Scalar ufunc tests should be using numpy scalar object to ensure the same coercion behavior
`_compileinfos` used to be `overloads`.  It was changed in https://github.com/numba/numba/commit/c78a2eab0fd87536f8754290f644415466e0f16f.  But that breaks `inspect_types()`.  I added `_compileinfos` to revive `inspect_types()` and I don't want to change too much code.  We may not need all the information in `_compileinfos`.