Add an option to cipher swap partitions.
Add an option to cipher swap partitions.

! Not tested yet: cryptsetup depends on a missing
! udev binary.

git-svn-id: 71c8032c709790ec749031c4215f8515ac00dc5a@19131 70bd8c7a-acb8-0310-9f0d-9cc1c95dcdbb

bnordgren/nixos,bnordgren/nixos,bnordgren/nixos,bnordgren/nixos,bnordgren/nixos