docache support was broken since the Stone age. Not all the
loop types correctly supported it because it wasn't transparent
to them and required manual hackery. Now _setup_livecd_content
transparently configures LOOP_PATH if docache is enabled.
It is now possible to pass multiple crypt_roots= and crypt_swaps=
parameters (mind the "s") and have multiple devices concurring to
building the final root device and swap areas activated.
The change is backward compatible and crypt_root=, crypt_swap= is
still fully supported.
This change makes possible to support multiple device mapper block
devices grouped together into aggregated software raid devices.
For instance, two individual luks devices can be now used to build
a single raid0 or raid1 md device.
Moreover, genkernel-next initramfs now supports multiple encrypted
swap devices.