orts. Since port specific information is in appropriate arch/.../md.h
bsddisklabel.c is currently #included by arch/.../md.c.
I'm not totally happy about this, but my concience is somewhat salved by the
overall reduction in breakage.
Initially only pmax, sparc, vax and x68k are using bsddisklabel.c.
While I'm here adjust defs.h for more than eight partitions in a generic
fashion.