Rework OPTIONs handling in Qt 5.9.3.

qtmultimedia now uses a configure.json file to describe configuration options
and checks that qmake should perform. On the one hand it means
extrapatch-no-gstreamer no longer applies (and neither does the TBR_DEPENDS
hack in the Makefile), on the other the configuration process has been
streamlined: we only need to pass the right options via QMAKE_CONFIGURE_ARGS to
enable and disable options.

While here, stop setting QT_DEFINES altogether in the Makefile, as none of them
are really necessary at all:

• XVIDEO is a Qt4 thing;
• ALSA, OPENAL and PULSEAUDIO are handled by qmake's configure.json infrastructure, which sets a QT_NO_<OPTION> macro in qtmultimedia-config.h when they are not enabled.
• There is no QT_{NO_}GSTREAMER upstream, so we're basically defining some macros that no code is going to use.

Reviewed by: tcberner (earler version without the QT_DEFINES changes)