PostgreSQL: Fix syntax error in page_props index

PostgreSQL: Fix syntax error in page_props index

Follows up I217c42656fb877ff35a36eb446a22bdaf119faac

That change introduced a syntax error during update.  I have verified
that this fixes the syntax problem so that update.php runs, but have
not verified that the new functionality behaves as intended.

Also, the PostgreSQL schema changes introduced during the update
process were not present at all in a fresh install to PostgreSQL.  Add
analogous changes to tables.sql.

Bug: 64807
Change-Id: I736344839ec478216402fdfe260968afbd663498