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

Add support for our own DTrace scripts and those from the DTraceToolkit
to the build system. FreeBSD written scripts are stored in
src/share and the toolkit scripts are brought from the cddl directory
into a working tree via install.

MFC after: 2 weeks