Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

MFC: 235380,235454,235455,235456,235457,235613,235614,235628,236567,
238125,238535,238660,238979,239972

Bring all changes to the DTrace Toolkit into FreeBSD 9.

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