Revision 465529

Update multimedia/mythtv and related ports to 29.1 [1]

Convert multimedia/mythtv-frontend to a slave port of multimedia/mythtv
which should make future updates much easier.

Upstream security patches have been added to address known
vulnerabilities in the bundled ffmpeg 3.2.

PR:		225652 (initial patches to update to 29.0) [1]
Submitted by:	<lucylangthorne55@gmail.com> [1]
Differential Revision:	https://reviews.freebsd.org/D14563