The @by_ref qualifier is now allowed on parameters, returns and
struct fields in the usual qualifier section. It will mean that
this type is passed around by reference, and will only be allowed
on types that are not already pointer-like.
The @move qualifier will replace @owned as one with a clearer
meaning. It means "transfer of ownership". It has the same semantics
as the current @owned, i.e. on return values it transfers ownership
of the value to the caller, on parameters it transfers ownership
to the callee (the inverse is the default when not specified).
On struct fields, it means the field will transfer together with
the struct that contains it.
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