Update devel/libdbusmnenu-qt and devel/libdbusmenu-qt5 to a newer snapshot.

• Update them both to 0.9.3.160420160218
• While doing so, make devel/libdbusmenu-qt5 a slaveport

Reviewed by: rakuco, mat
Approved by: rakuco (mentor)
Differential Revision: https://reviews.freebsd.org/D7895