[dev-qt/qtgui:5] Fix session management (bug 518262)

Package-Manager: portage-2.2.10
[qt5-build.eclass] QCONFIG_* variables are no longer public API.
[dev-qt/qtgui:5] Simplify dbus handling.

qt5_base_configure already passes -no-dbus, no need to repeat it here.

Package-Manager: portage-2.2.10
[dev-qt/qtnetwork:5] Simplify dbus and ssl handling.

qt5_base_configure already disables both by default, DRY.

Package-Manager: portage-2.2.10
[dev-qt/qtwidgets:5] Introduce some USE flags to keep consistency with qtgui.

Should fix the crashes reported by Franz Fellner in bug 518262#c2

Package-Manager: portage-2.2.10
[dev-qt/qtmultimedia] Fix (automagic) dependencies

Fixes bug #517532

Package-Manager: portage-2.2.10