This patch introduces the Genode::raw function that prints output
directly via a low-level kernel mechanism, if available.
On base-linux, it replaces the former 'raw_write_str' function.
On base-hw, it replaces the former kernel/log.h interface.
Fixes#2012
This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.
Issue #1082