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

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

Teach truss about 32-bit FreeBSD and Linux binaries on amd64. Some
additional work is needed to handle ABI-specific syscall argument parsing,
but this gets the basic tracing working.

MFC after: 1 week