I wrote:
> It looks like the MSVC build scripts are cheating by not copying
> parser/gram.h into the include tree where it should be. I'm not
> entirely sure why that has worked at all in the past, but it's
> not working any more.
On further consideration, it's probably not a good idea to let
plpgsql depend on gram.h anyway --- in the past we've taken measures
to confine the use of that file as narrowly as possible. I did a
bit of code refactoring instead.
regards, tom lane