Changed our internal representation of the PostgreSQL version from tuples to
integers as used by libpq and psycopg2. This simplifies version comparison
operations.
Also, using the associated libpq/psycopg2 API allows to remove the need for
manually issuing in-band ``SELECT version()`` SQL queries to obtain the server
version (or at least reduce its number if version of psycopg2 in use is older
than 2.0.12). Refs #10509.
git-svn-id: http://code.djangoproject.com/svn/django/trunk@16439 bcc190cf-cafb-0310-a4f2-bffc1f526a37