zsh: Change from 4.3.17 to 5.0.0, which is the latest stable release. Also...

zsh: Change from 4.3.17 to 5.0.0, which is the latest stable release. Also change the mirror from the zsh ftp server, which is really slow and unstable, to a sourceforce mirror.

The reason for removing the 4.3.17 recipe is that it used the ftp mirror, which
has removed the 4.3.17 tarbal used.

Signed-off-by: Martin Ertsaas <mertsas@cisco.com>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>