where is the locale set for each server instance?

Hi!

I'm pluggin ICU into PostgreSQL for unicode collation, since FreeBSD has no
support for unicode collation. It works fine, but I cannot find out where
to set the default locale for each backend instance. I want to use the
LC_COLLATE used in initdb, now I've just hard wired it for my own needs. I
tried backend/access/transam/xlog.c:ReadControlFile, but it is not
sufficient.

in backend/main/main.c:
    /*
     * Set up locale information from environment.    Note that LC_CTYPE and
     * LC_COLLATE will be overridden later from pg_control if we are in an
     * already-initialized database.

So, I'm trying to find out where LC_COLLATE is overridden. Any tips?

Thanks,
Palle