Re: Extension Enhancement: Buffer Invalidation in pg_buffercache

[Sorry to those who received this message twice -- the first time got
bounced by the list because of a defunct email address in the CC
list.]

Here is a rebase of Palak's v2 patch. I didn't change anything except
for the required resource manager API change, a pgindent run, and
removal of a stray file, and there is still some feedback to be
addressed before we can get this in, but I wanted to fix the bitrot
and re-open this CF item because this is very useful work. It's
essential for testing the prefetching-related stuff happening in
various other threads, where you want to be able to get the buffer
pool into various interesting states.