PowerPC specific directory(Re: PowerMac types.h lossage)

[sakamoto%cec.co.jp@localhost (Kazuki Sakamoto)]

Because NetBSD/macppc was merged,
this is a good opportunity to do the following thing.

1. present sys/arch/powerpc directory is changed to sys/arch/ofppc
   (ofwppc, and so on).
2. make PowerPC specific directory(sys/arch/powerpc or sys/cpu/powerpc)
   as mips,m68k.

Any thoughts?

Kazuki Sakamoto
sakamoto%cec.co.jp@localhost