BUG #2536: TInterval: wrong interpretation of "Undefined Range" value.

The following bug has been logged online:

Bug reference: 2536
Logged by: Alexandr Sereda
Email address: click2002(at)ukr(dot)net
PostgreSQL version: 7.4.9 - 8.1.4
Operating system: FreeBSD, Linux, Windows Xp
Description: TInterval: wrong interpretation of "Undefined Range"
value.
Details:

Then we store some values in tinterval fields, psql shows "Undefined Range".
Then we dumping table with these values, we receive same in dump. But, then
we wont to restore it back, we receive error.

TINTERVAL
====================================================
BASE DUMP OPERATION
----------------------------------------------------
UNDEFINED RANGE --> UNDEFINED RANGE DUMPING OUT

UNDEFINED RANGE <-- INVALID DUMPING IN
====================================================