Backport removal of legacy platforms and drivers from master

[morozov]

Q	A
Type	improvement
BC Break	yes

Removed platforms and drivers:

1. PostgreSQL <9.3, SQL Server < 2008, SQL Anywhere < 16, PDO-based IBM DB2 driver (Drop support for legacy platforms #3055).
2. Drizzle (Drop Drizzle support #3040).
3. Azure and sharding (Remove support for sharding and the Azure platform #3602).
4. PostgreSQL 9.3, MariaDB 10.0 (Drop db support for PostgreSQL 9.3 and MariaDB 10.0 #3477).
5. SQL Server 2008 (Dropped SQL Server 2008 support #3756).

TODO:

• Makes sure it will cleanly merge back to master as a validation of the proper backport.
• Once this is merged, update the milestones of the backported PRs and the corresponding issues.