Restoring the superuser account on the postgres server
Superuser rights aren't in any config file, they're part of the pg_catalog.pg_authid database table, which is shared between all databases in a PostgreSQL install.

You  need to stop the PostgreSQL server, then restart it in single user mode, where it's always running as superuser. 

There, you can ALTER USER myuser SUPERUSER to grant superuser rights. Exit single user mode, and start the server back up.

The exact details are a little distro and version dependent, but something like:

service postgresql stop
sudo -u postgres postgres --single /var/lib/pgsql/9.1/main/data

ALTER USER postgres SUPERUSER;

(control-D to exit)

service postgresql start


On some systems you might need to use an explicit path to the postgres executable, like /usr/pgsql-9.1/bin/postgres. Again, paths may vary based on version and distro.