quik: buildable under squeeze

A few large changes:
1) removed the need for ext2fs lib, the
   new ext2fs implementation comes from u-boot
   and gives symlink support for free.
2) cleaned up sources a bit, cleaning up
   the entire disk/file/part access code quite
   a bit

Signed-off-by: Andrei Warkentin <andrey.warkentin@gmail.com>