multimedia/mlt:

• Update to 6.2.0
• Mark KDE4 option as implying/requiring QT4 option
• Move USE_KDE4=kdelibs to new options helpers
• Add USE_GNOME=cairo as notified by new stage-qa error

Changes this release:

http://mltframework.blogspot.fr/2016/04/version-620-released.html
http://mltframework.blogspot.fr/2016/02/version-600-released.html
http://mltframework.blogspot.fr/2015/07/version-098-released.html

This update also allows multimedia/mlt to build against ffmpeg 3.0.x.
The ports tree currently still has multimedia/ffmepg at version 2.8.7,
however this update is backwards compatible with ffmpeg 2.8.7. The
update of multimedia/ffmpeg to 3.0.x branch is waiting for ports which
depend on it to successfully build with the newer version of ffmpeg.

PR: 207390
Submitted by: olivierd
Approved by: avilla (maintainer timeout), mat (mentor), makc, araujo (with kde hat)
Differential Revision: https://reviews.freebsd.org/D6754