[New Port] sysutils/dwatch-gource

DTrace modules for FreeBSD dwatch(1) to produce gource logs. Gource
(graphics/gource) is a tool normally used for visualizing source control
revisions, but it can also be used for visualizing process trees, filesystem
activity, syscall access, and more.

These modules allow you to generate log files for rendering realtime process,
filesystem, and other activities in FreeBSD using gource.

Reviewed by: imp (mentor; earlier version), mat (mentor)
Approved by: mat (mentor)
Sponsored by: Smule, Inc.
Differential Revision: https://reviews.freebsd.org/D15407