adodb: check for Postgres 8.1

See Eduforge #2318 or LP #547951.

Bug 1384473

(cherry picked from commit 4bdafccba511540e6db92277aa104a23f57209ac)

Change-Id: I0e38e7f4f4e8da35f6c9f8e728213c2218e9a36f
Signed-off-by: Francois Marier <francois@catalyst.net.nz>
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>