fix csum calculation and update checksums

fix csum calculation and update checksums

it was intended to be a rol instead of a simple left shift which changes the
checksums for the various programs (like 'proxprox', 'postfix/postscreen',
etc.) so we update those and use defines instead of the hardcoded hex values.
this makes it much more readable and less error prone

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>