BUG #11523: Regular expressions work differently on different platforms

The following bug has been logged on the website:

Bug reference:      11523
Logged by:          Daniel Migowski
Email address:      dmigowski@ikoffice.de
PostgreSQL version: 9.1.2
Operating system:   Debian Linux 6.0.6 + Windows 7
Description:

I recently found that regular expressions, or specifically the [:space:]
shorthand escape work differntly on Windows and Linux. On Linux the
non-brakeable space is not included in the shorthand escape, on windows it
is. The following statement is therefore true on Windows and false on
Linux:

    select convert_from(E'\\xA0'::bytea,'ISO8859-1') ~ '\s'

This brakes email validation here, and the insert of a linux created backup
into my windows machine. Is it possible to fix that? Is there a reason that
UTF-8 on Linux differs from UTF-8 on Windows?