that were added to sparc64 and later powerpc, really should have been in the MI area. But changing that now with insufficient preperation will just cause too much pain. Move MD_FETCH() to the MI sys/linker.h file to avoid another two copies of it.
kernel text and data from the loader to the kernel, so that the tte format is not part of the loader->kernel ABI.
machdep.c. - Adapt to critical_* changes.
