The kernel space parts of standard system header files were protected
against misuse by a preprocessor error directive. This approach does
not work well with tools such as Doxygen. Provide the kernel space
items only if the required defines are present.
Move the kernel space content of some Newlib provided header files to
RTEMS and libbsd. This allows to use the Newlib provided header files
with different FreeBSD baselines.
Update #3472.