Fix for truly nasty bug introduced this morning

[Hal Murray]

> The mistake I made was putting the new field first in the structure. This
> caused it to be randomly trashed by type-punning dynamic-allocation code
> that was expecting a link field there. 

I don't understand yet.  Why are we type punning there?  If it's a hack to 
avoid malloc, why is the caller assuming anything about the state of the new 
storage?

Should we make a cleanup pass at all avoid-malloc hacks?

-- 
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