bug#32405: Turning misc objects into pseudovectors

[Paul Eggert]

Paul Eggert wrote:
> > There is also a potential issue in terms of the resulting heap size of
> > markers (which may bump up from 6 words to 8 words, IIRC, unless your
> > patch does something to keep it down to 6)
>
> On a 64-bit platform the heap size of markers does not grow. The old size is 6 
> words (sizeof (union aligned_Lisp_Misc) is 48), and the new size is also 6 words 
> (sizeof (struct Lisp_Marker) is also 48).

I should have written that these numbers are for x86-64 on Fedora 28. They might 
differ on other 64-bit platforms, due to alignment issues.