Fix machine/ includes

Fix wrong checksum calculations of 32 bit unaligned two byte payloads.
Analyzed in PR port-mips/43882, but applied slightly different patch.
Also put some changes for readability.

Note netbsd-5 doesn't use this MD version but netbsd-4 needs a pullup.
(though it's unclear if it's really faster even on modern aggressive gcc4)

branches: 1.13.48; 1.13.66; 1.13.68; 1.13.70;
Remove duplicate #includes, patch contributed in private mail
by Slava Semushin <slava.semushin@gmail.com>.

To verify that no nasty side effects of duplicate includes (or their
removal) have an effect here, I've compiled an i386/ALL kernel with
and without the patch, and the only difference in the resulting .o
files was in shifted line numbers in some assert() calls.
The comparison of the .o files was based on the output of "objdump -D".

Thanks to martin@ for the input on testing.

branches: 1.12.8; 1.12.12;
Increment to the next byte after fetching.

Spotted by Dan Krejsa.

branches: 1.11.4; 1.11.6; 1.11.8; 1.11.10; 1.11.12;
merge ktrace-lwp.

branches: 1.10.16;
__KERNEL_RCSID()

branches: 1.9.6;
be friendly with gcc-3.1.1 -O2, which takes advantage of ANSI C
pointer aliasing rule (gcc optimization/7427). from tsubai, sync w/kame

Use the current MIPS in_cksum for in4_cksum too.

branches: 1.7.6;
ANSIfy.

branches: 1.6.6;
Fix for single-byte mbufs.

branches: 1.5.16;
Nuke register and remove trailling white space.

branches: 1.4.12;
Finish bi-endian support: add code to sum odd start/end bytes
correctly on both big and little endian systems.
From Tsubai Masanari <tsubai@iri.co.jp> in PR# 4434.

branches: 1.3.4;
Fix for mbufs that start on odd-byte-aligned boundaries, and use.

branches: 1.2.2;
Fix for chains containing interior mbufs with odd length.

mips-tuned bcopy from Jon Kay (UCSD) released under BSD copyright,
with standard BSD in_cksum() interface by Jonathan Stone.