Fix support for empty address groups (RFC822)
Fix support for empty address groups (RFC822)

This fixes support for address groups like 'Undisclosed recipients:;'
and solves errors like:

  [ERROR] z_RFC822 error: Empty group.
  [WARN] SyncObject->Check(): object from type SyncMail: parameter 'to'
      contains an invalid email address 'undisclosed-recipients:;'.
      Address is removed.

Empty address groups are fine according to RFC822. The file
z_RFC822.php was copied from the PEAR package Mail which has had a tiny
revival attempt called the 'Mail2' package. In this new package, two
RFC822 bugs were squashed.

z_RFC822 is now synced with the Mail2_RFC822 class.

mta59066/Z-Push-contrib,fmbiete/Z-Push-contrib,Freeaqingme/Z-Push-contrib,RavenB/Z-Push-contrib