This patch eliminates calls of 'cmpxchg' prior enabling the MMU. This is
needed because the 'ldrex' and 'strex' instructions do not always work
with MMU and L1 cache disabled, i.e., on Raspberry Pi.
Merge core only libs into the target make-files.
Use base-hw specific Board drivers that inherit
from generic Board_base.
Use Page_flags::access_t instead of additional
page_flags_t.
Fix#570
Instead of allocating and freeing the space that is needed for the
kernel thread objects from core, wich is not convenient with the
quota system, platform thread now holds the space as array by
itself.
Unfortunately we cannot measure the space size by a static function
anymore, so kernel thread had to be moved from kernel.cc into its
own header. This way platform thread can use sizeof().
Fix#543
