Although there remains some debate about how CREATE TYPE should represent
the collation property, this doesn't really affect what we need to do in
citext's script, so go ahead and fix that.
This isn't fully tested as yet, in particular I'm not sure that the
"foo--unpackaged--1.0.sql" scripts are OK. But it's time to get some
buildfarm cycles on it.
sepgsql is not converted to an extension, mainly because it seems to
require a very nonstandard installation process.
Dimitri Fontaine and Tom Lane