Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFppc64:

Kernel sources for 64-bit PowerPC, along with build-system changes to keep
32-bit kernels compiling (build system changes for 64-bit kernels are
coming later). Existing 32-bit PowerPC kernel configurations must be
updated after this change to specify their architecture.

/* -> /*- for license, minor formatting changes

Missed odd address test when transcribing the Alpha version.
This fixes the checksum problems seen with telnet.

in_cksum et al.

Submitted by: Peter Grehan <peterg@ptree32.com.au>