Fix yet another typo in comment.

Etsuro Fujita
Don't pass NULL to fprintf, if a bogus connection string is given to pg_dump.

Back-patch to all supported branches.
Fix pg_dumpall with database names containing =

If a database name contained a '=' character, pg_dumpall failed. The problem
was in the way pg_dumpall passes the database name to pg_dump on the
command line. If it contained a '=' character, pg_dump would interpret it
as a libpq connection string instead of a plain database name.

To fix, pass the database name to pg_dump as a connection string,
"dbname=foo", with the database name escaped if necessary.

Back-patch to all supported branches.
Add postgres_fdw contrib module.

There's still a lot of room for improvement, but it basically works,
and we need this to be present before we can do anything much with the
writable-foreign-tables patch.  So let's commit it and get on with testing.

Shigeru Hanada, reviewed by KaiGai Kohei and Tom Lane
Teach MSVC build system about postgres_fdw.

Per buildfarm.
Need to decorate XactIsoLevel as PGDLLIMPORT for postgres_fdw.

Per buildfarm.
Remove useless variable

Per Jeff Janes