Update Qt5 ports to 5.9.3.
This took quite a lot of time because Qt's own build system underwent
several changes in 5.8.0 that took a while to adapt to.
And, of course, qt5-webengine is a behemoth that we need to patch like crazy
due to its bundling of Chromium. In fact, most of the Chromium patches in
qt5-webengine have been imported with no changes from www/chromium@433510
("www/chromium: update to 56.0.2924.87").
New port: accessibility/qt5-speech
Bigger changes to Qt5 ports we had to make:
- Qt now allows using a configure.json file to define configuration options
and specify configuration checks that can be done when qmake is invoked.(Only the first 15 lines of the commit message are shown above )