title: rake db:structure:dump fails under PostgreSQL / Rails 3.2
body: <p>I get this error message:</p>
  
  <pre>
  pg_dump: too many command-line arguments (first is "demo_db")
  Try "pg_dump --help" for more information.
  rake aborted!
  Error dumping database
  
  Tasks: TOP => db:structure:dump
  (See full trace by running task with --trace)
  </pre>
  
  <p>This used to work under Rails 3.1. I'm using Rails 3.2.3 and PostgreSQL 9.0.5. Other tasks like db:migrate or db:rollback work just fine.</p>