bug#32405: [PATCH] Turn misc objects into pseudovectors

[Paul Eggert <eggert@cs.ucla.edu>]

> If the patch makes the interpreter simpler that sounds worthwhile, but
> are you sure there is a meaningful performance difference ? 0.3% sounds
> lost in the noise. What is the time/space impact on 32bit bit platforms ?

0.3% is too small for most people to notice, yes. It is a significant difference 
only in the sense that I can reproduce it reliably on my 64-bit platform (Fedora 
28, x86-64, AMD Phenom II X4 910e (2010)). I have not measured the effect on 
other platforms. I expect it would be a similarly small number. The main point 
of this patch is simplification and allowing for other uses of the tag, not 
performance.

> Integration of this patch and the bignum feature branch into master may
> both need some time to stabilize. Please discuss with Eli and Tom to
> agree which is merged first, and allow time for master to reach a stable
> state before the second of them is merged.

I don't care whether this patch lands before or after bignum. If it lands 
second, I will resolve any incompatibilities; they won't be major. If it lands 
first I can help with any needed changes on the bignum side. I don't want either 
of us to be waiting for the other, though, and this patch is ready to go in now.