Comment 83 for bug 953875

Created attachment 115162
cryptsetup: Implement offset and skip options

parse_size() is not appropriate here, as the offset=/skip= argument is a plain natural number, and the unit is always "512 byte blocks". So allowing things like "3.3K" there would be confusing, wrong, imprecise, and incompatible with the cryptsetup project.

I added documentation, the initializer, and also incorporated warning that Zbigniew suggested on the ML.