PostgreSQL 7.3 is _not_ supported

1) includes/database.pgsql.inc uses SHOW SERVER_VERSION to determine which postgresql version we're running, but that statement was only introduced in 7.4.
Fix: none that I know.

2) modules/system/system.install tries to define three domains with range checks (the unsigned integer types); range checks on domains were introduced in 7.4.
Fix: none that I know.

3) modules/system/system.install contains an 'ALTER SEQUENCE ... MINVALUE 2 RESTART 2' statement, which was introduced in 7.4.
Fix: use SELECT setval('...', 2). In 7.3 there is no way to set a sequence's min_value after its creation, but I don't think there are any reasons to either...

4) modules/system/system.install defines some functional indexes (indexes on functions of columns). Functional indexes support is very crude in 7.3 and does not allow functions taking other arguments than the column name, or mixing functions and simple columns as keys. 7.4 should be ok in this regard.
Fix: none that I know of.

Since I am just doing a test install of drupal none of this issues is a real showstopper to me; however I think that the minimum PostgreSQL version in the requirements page should be upgraded to 7.4.