upstreaming `norm_cast`

Stream: std4

[Scott Morrison]

I would like to upstream norm_cast to Std. Does this seem reasonable? (It should not be particularly difficult.)

[Scott Morrison]

I would like to see if I can make zify more powerful and be able to use it (rather than writing a close cousin) for omega.

[Mario Carneiro]

I think norm_cast is already half-upstreamed, the attribute is defined upstream