BUG #6015: to_hex and negative integer

The following bug has been logged online:

Bug reference:      6015
Logged by:          Marco Spiga
Email address:      ctxspi@gmail.com
PostgreSQL version: 8.3.12
Operating system:   Ubuntu Linux on kernel version 2.6.30.5
Description:        to_hex and negative integer
Details:

Hi!
First, thank for your excellent software.
My question is:
Why when I try: SELECT to_hex(-1)
it give me a strange result: ffffffff


Thanks Again