Renaming MemoryContextResetAndDeleteChildren to MemoryContextReset

We've discussed doing $SUBJECT off and on for nearly ten years,
the oldest thread I could find about it being here:
http://www.postgresql.org/message-id/flat/1186435268(dot)16321(dot)37(dot)camel(at)dell(dot)linuxdev(dot)us(dot)dell(dot)com
It's come up again every time we found another leak of dead child
contexts, which happened twice last year for example. And that patch
I'm pushing for "expanded" out-of-line objects really needs this to
become the default behavior anywhere that we can detoast objects.

So attached is a patch to do it. I've verified that this passes
"make check-world", not that that proves all that much :-(

I did not make an attempt to
s/MemoryContextResetAndDeleteChildren/MemoryContextReset/ globally,
as it's certainly unnecessary to do that for testing purposes.
I'm not sure whether we should do so, or skip the code churn
(there's about 30 occurrences in HEAD). We'd want to keep the
macro in any case to avoid unnecessary breakage of 3rd-party code.

Thoughts? Any objections to pushing this?

regards, tom lane