Generalized (taint-like) attributes (was Re: RFC 258)

[John Porter]

Tom Christiansen wrote:
> 
> You want to have more properties that work like tainting does: a
> per-SV attribute that is enabled or disabled by particular sorts
> of expressions, sometimes dependent upon the previous presence or
> absence of that property, other times, not so.

While we're at it, let's unify this with the attribute system
we have.  We'd like to be able define new attributes, get and
set their values, and attach behaviors to their access.
We have been assured that this should be easy to do in user code.

-- 
John Porter