multimedia/mlt: Fixes post r416546 commit

[woodsb02]

Summary

multimedia/mlt:

• USE_GNOME=cairo only applies when SWFDEC option is enabled
• USE_XORG=x11 applies even with all options disabled (due to SDL)
• USE_GNOME=glib20 is required when JACK or SWFDEC options are enabled
• Fix pkg-plist: filter_audiospectrum.yml only installed if QT4 enabled

Test Plan

poudriere testport multimedia/mlt

[woodsb02]

Thanks to mat for prompting me that USE_GNOME=cairo may only be required if certain options are enabled

[adamw]

In the commit message, be sure to note that this is a follow-up to the previous commit and that the maintainer timeout applies to this commit as well.

[woodsb02]

Bump PORTREVISION due to dependency changes (as notified by mat)

[mat]

You don't need the maintainer timeout thingie here, it does fall into the portmgr blanket :-)