pefs status report 2

[Gleb Kurtsou]

Hi,

This week I've spent adding some basic crypto-related functionality into
pefs. I've implemented support file name encryption and data encryption.
Although it's rather limited at the moment: vop_lookup should be changed
to perform encrypted name lookup in cache and/or using readdir, as
encrypted name can't be derived from plain text name for lookup;
read/write do not enforce reading/writing on block boundaries.
Currently I'm working on fixing it and adding support for the rest of
vnode operations.