Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

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

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

Upgrade xz to git snapshot as of 20101010

Approved by: delphij (mentor)
MFC after: 1 month

Add two public headers missing in r207842
Adjust CFLAGS for lzmainfo, xz, xzdec

Approved by: delphij (mentor)
MFC after: 2 weeks

Import of liblzma, xz, xzdec, lzmainfo from vendor branch
Add support for xz and lzma to lesspipe.sh (xzless, lzless)
Bump __FreeBSD_version

Approved by: delphij (mentor)
MFC after: 2 weeks