Re: Better testing coverage and unified coding for plpgsql loops

However, while I was doing that, it seemed like the tests I was adding
were mighty repetitive, as many of them were just exactly the same thing
adjusted for a different kind of loop statement.  And so I began to wonder
why it was that we had five copies of the RC_FOO management logic, no two
quite alike.  If we only had *one* copy then it would not seem necessary
to have such duplicative test cases for it.  A bit of hacking later, and
I had the management logic expressed as a macro, with only one copy for
all five kinds of loop.  I verified it still passes the previous set of
tests and then removed the ones that seemed redundant, yielding
plpgsql-unify-loop-rc-code.patch below.  So what I propose actually
committing is the combination of these two patches.