Support `align(default)`

[0xEAB]

Upstream D has plans to support align(default) in the future: https://github.com/dlang/dmd/issues/20587 https://github.com/dlang/dmd/pull/20589

At the moment, I’m getting the following errors with serve-d on the upstream test file:

struct S
{
    align(1)
    {
        short x1;
        int y1;
        long z1;

        align(default) /* Primary expression expected */
        { /* declaration expected instead of `{` */
            short x;
            int y;
            long z;
        }
    }
}