gnu: qt: Update to 5.9.0.

* 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 5.9.0.
(qtbase)[source]: Remove bundled freetype, libpng, libjpeg, pcre2, xcb,
xkbcommon, zlib.
[inputs]: Remove pcre, add pcre2.
[arguments]: Add configure flag to use system pcre, update flag to not
compile examples.
(qtwayland)[source]: Remove examples in a snippet.
(qtlocation)[inputs]: add icu4c, openssl, zlib.