Re: Constant Splitting/Refactoring

Here is a version 2 of this patch, rebased atop 97d85be365.

As before, this is a cleanup/prerequisite patch series for the page
features/reserved page size patches[1]. (Said patch series is going
to be updated shortly.)

This splits each of the 4 constants that care about page size into
Cluster-specific and -Limit variants, the first intended to become a
variable in time, and the second being the maximum value such a
variable may take (largely used for static
allocations).

Since these patches define these symbols to have the same values they
previously had, there are no changes in functionality. These were
largely mechanical changes, and as such we should perhaps consider
making the same changes to back-branches to make it so context lines
and the like
would be the same, simplifying maintainer's efforts when applying code
in back branches that touch similar areas.

The script I have to make these changes is simple, and could be run
against the back branches with only the comments surrounding Calc()
pieces needing
to be adjusted once.

Thanks,

David

[1] https://commitfest.postgresql.org/47/3986/