In the `MY THAT'S GROSS' department...
Eliminate the recursive include of machine/endian.h from sys/endian.h.

Foolish consistency. Mainly, always use underscores and sys/endian.h.

Include <sys/endian.h> after defining whether where are little- or
big-endian. i386, pc532 and vax still include <machine/byte_swap.h>
and define macros for the {n,h}to{h,n}*() functions. mips also

Include <sys/endian.h> after defining whether where are little- or
big-endian. i386, pc532 and vax still include <machine/byte_swap.h>
and define macros for the {n,h}to{h,n}*() functions. mips also
defines some endian-independent assembly-code aliases for unaligned
memory accesses.

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Mark [hn]to[nh][ls]() with __const__, so they are subject to CSE.

Move the bswap functions from libutil to libc (this bups the
minor of libc and the major of libutil). For little-endian architectures
merge the bnswap() assembly versions with nto* and hton* using sy

Move the bswap functions from libutil to libc (this bups the
minor of libc and the major of libutil). For little-endian architectures
merge the bnswap() assembly versions with nto* and hton* using symbols
aliasing. Use symbol renaming for the bswap function in this case to avoid
namespace pollution.
Declare bswap* in machine/bswap.h, not machine/endian.h. For little-endian
machines, common code for inline macros go in machine/byte_swap.h
Sync libkern with libc.
Adjust #include in kernel sources for machine/bswap.h.

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(Always) (practice) (safe) (macro expansion).

Import of sparc64.