BUG #5386: HBA rejection error message incorrect

The following bug has been logged online:

Bug reference:      5386
Logged by:          Bryan Henderson
Email address:      bryanh@giraffe-data.com
PostgreSQL version: 8.4.3
Operating system:   Linux
Description:        HBA rejection error message incorrect
Details:

The two usernames are reversed in the error message "provided username (foo)
and authenticated username (bar) don't match".

src/backend/libpq/hba.c:1676