Log Message:
Import PostgreSQL 9.0 binary upgrade tool as databases/postgresql90-upgrade

pg_upgrade (formerly called pg_migrator) allows data stored
in PostgreSQL data files to be migrated to a later PostgreSQL
major version without the data dump/reload typically required
for major version upgrades, e.g. from 8.4.7 to the current
major release of PostgreSQL. It is not required for minor
version upgrades, e.g. from 9.0.1 to 9.0.4.