gnu: qt: Update to 5.8.0.

gnu: qt: Update to 5.8.0.

* gnu/packages/qt.scm (qtbase, qtsvg, qtimageformats, qtx11extras,
qtxmlpatterns, qtdeclarative, qtconnectivity, qtwebsockets, qtsensors,
qtmultimedia, qtwayland, qtserialport, qtserialbus, qtwebchannel,
qtlocation, qttools, qtscript, qtquickcontrols, qtquickcontrols2,
qtgraphicaleffects, qtgamepad, qtscxml, qtpurchasing, qtcanvas3d,
qtcharts, qtdatavis3d, qtwebkit): Update to 5.8.0.
(qtdeclarative-render2d)[properties]: New field, package has been
absorbed by qtdeclarative and thus marked as superseded by it.