synergy: Update to new upstream version 1.5.1.

Bugfix release, fixing the following bugs:

 - Configuration file paths containing spaces don't work
 - Log path needs to be in quotes on windows
 - Installer fails when Windows Firewall is disabled

http://svn.synergy-project.org/tags/1.5.1/ChangeLog

Signed-off-by: aszlig <aszlig@redmoonstudios.org>