devel/libayatana-indicator: Add new port

The Ayatana Indicators project is the continuation of Application Indicators
and System Indicators, two technologies developed by Canonical Ltd. for the
Unity7 desktop.

Application Indicators are a GTK implementation of the StatusNotifierItem
Specification (SNI) that was originally submitted to freedesktop.org by KDE.

System Indicators are an extensions to the Application Indicators idea.
System Indicators allow for far more widgets to be displayed in the
indicator's menu.

The Ayatana Indicators project is the new upstream for application
indicators, system indicators and associated projects with a focus on making
Ayatana Indicators a desktop agnostic technology.

On GNU/Linux, Ayatana Indicators are currently available for desktop
envinronments like MATE (used by default in Ubuntu MATE), XFCE
(used by default in Xubuntu, LXDE, and the Budgie Desktop).

The Lomiri Operating Environment (UI of the Ubuntu Touch OS, formerly known as
Unity8) uses Ayatana Indicators for rendering its notification area and the
UBports project is a core contributor to the Ayatana Indicators project.

WWW: https://github.com/AyatanaIndicators/libayatana-indicator