Alex, I used `pu` to mean `page union` (it's not required, we could use a naked `fix_recno`, but I thought the `pu` made collisions less likely.

I don't worry about changing names in the future: I'm sure we will, but there's no risk of introducing bugs because code just won't compile.   Macros have the same problem, right?  (Unless the macro didn't include the underlying field name, which it almost certainly would?)

I prefer `pu_fix_recno` to `u.col_fix.recno`; I suspect I'd prefer `page->pu_fix_recno` to `WT_PAGE_FIX_RECNO(page)`, too, but I can't think of any solid arguments pro or con.

Anyway... I figured this would be an annoying change, I'm happy to defer to the group consensus, unless someone can come up with a technical argument in one direction or the other.

@sueloverso, @michaelcahill