DATA_ALIGNMENT vs. DECL_USER_ALIGNMENT

[Robert Dewar]

> No, that's actually OK since it is the property of the macros that
> modify alignment that if you start with the alignment that they
> produced, they produce that alignment again.  I suppose nobody has
> even formally documented this property, but it would be very hard to
> see why they would do anything else.

Well indeed it should be formally documented if we depend on it. But
in that case, I also see no harm in setting a "user defined" alignment
that corresponds to this default value.