- Honer MK_KERBEROS for Heimdal rc.d scripts.
- Add rc.c/kerberos to OLD_FILES.
Only build the ARM tranpoline when KERNPHYSADDR is defined as it is
otherwise unneeded in armv6 kernels.

MFC after:	1 week
Allow the armv6 kernel to be build with PHYSADDR undefined. The kernel
will now find the virtual to physical mapping for libkvm to use at
runtime. This makes PHYSADDR redundant, however keep it around to give
everyone a chance to update their libkvm.

MFC after:	1 week