Fix spec wrt. the align attribute

[kinke]

The semantics were changed with dlang/dmd#6754.

Resolves https://issues.dlang.org/show_bug.cgi?id=20754.

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[veelo]

I am in favour of dlang/dmd#6754, but I don’t think the language should be changed silently (https://forum.dlang.org/post/dsklfejzyfmytckeuhby@forum.dlang.org). Since dmd has worked this way for more than three years now I guess one could argue that we have exceeded the deprecation period anyway, but I’m not sure everybody would see it that way. A change log entry would be in order, maybe?

[kinke]

A changelog entry for something that was changed/fixed 3 years ago? C'mon. The previous scheme was just plain wrong, resulting in stuff like T.alignof = 4, T.sizeof = 10 etc.

[Geod24]

I agree with @kinke , changelog entries are the burden of the PR that changes the behavior, not the ones that document it. If anything, it would be confusing to have it now.