This commit separates certain SMP aspects into 'spec/smp' subdirectories.
Thereby it simplifies non-SMP implementations again, where no locking
and several platform specific maintainance operations are not needed.
Moreover, it moves several platform specifics to appropriated places,
removes dead code from x86, and starts to turn global static pointers
into references that are handed over.
Instead of holding SPEC-variable dependent files and directories inline
within the repository structure, move them into 'spec' subdirectories
at the corresponding levels, e.g.:
repos/base/include/spec
repos/base/mk/spec
repos/base/lib/mk/spec
repos/base/src/core/spec
...
Moreover, this commit removes the 'platform' directories. That term was
used in an overloaded sense. All SPEC-relative 'platform' directories are
now named 'spec'. Other files, like for instance those related to the
kernel/architecture specific startup library, where moved from 'platform'
directories to explicit, more meaningful places like e.g.: 'src/lib/startup'.
Fix#1673
