BUG #4562: ts_headline() adds space when parsing url

The following bug has been logged online:

Bug reference: 4562
Logged by: Denis Monsieur
Email address: dmonsieur(at)gmail(dot)com
PostgreSQL version: 8.3.4
Operating system: Debian etch
Description: ts_headline() adds space when parsing url
Details:

My system is 8.3.4, but people in #postgresql with 8.3.5 have confirmed the
issue.

The problem is a space being added to text in the form of
http://some.url/path
Compare the output:

shs=# SELECT ts_headline('http://some.url', to_tsquery('sometext'));
ts_headline
-----------------
http://some.url
(1 row)

shs=# SELECT ts_headline('http://some.url/path', to_tsquery('sometext'));
ts_headline
-----------------------
http:// some.url/path
(1 row)