AWS Redshift Support

My attempt to provide support for Amazon Web Service Redshift database.

Redshift is based on PostgresSQL v.8.0 with unsupported features. Here is the list : http://docs.aws.amazon.com/redshift/latest/dg/c_redshift-and-postgres-sql.html

For the unit tests, I copied PostgresSQL tests and removed those testing unsupported features. Everything was green, except the locking test. Which I found no way to be less restrictive.

Marc-André