qt5multimedia: drop broken gstreamer 0.10 support

qt5multimedia: drop broken gstreamer 0.10 support

The gstreamer 0.10 support code seems to have bitrotten as the build fails
with undefined references to various functions:

.obj/qgstreameraudiodecodersession.o: In function `QGstreamerAudioDecoderSession::read()':
qgstreameraudiodecodersession.cpp:(.text+0x13a0): undefined reference to `QGstUtils::audioFormatForBuffer(_GstBuffer*)'
collect2: error: ld returned 1 exit status
Makefile:111: recipe for target '../../../../plugins/mediaservice/libgstaudiodecoder.so' failed
make[6]: *** [../../../../plugins/mediaservice/libgstaudiodecoder.so] Error 1
Makefile:45: recipe for target 'sub-audiodecoder-make_first' failed
make[5]: *** [sub-audiodecoder-make_first] Error 2
make[5]: *** Waiting for unfinished jobs....
.obj/qgstreamercapturesession.o: In function `QGstreamerCaptureSession::probeBuffer(_GstBuffer*) [clone .part.30]':
qgstreamercapturesession.cpp:(.text+0x3fc8): undefined reference to `QGstUtils::bufferToImage(_GstBuffer*)'
collect2: error: ld returned 1 exit status
Makefile:153: recipe for target '../../../../plugins/mediaservice/libgstmediacapture.so' failed
make[6]: *** [../../../../plugins/mediaservice/libgstmediacapture.so] Error 1
Makefile:95: recipe for target 'sub-mediacapture-make_first' failed
make[5]: *** [sub-mediacapture-make_first] Error 2
.obj/qgstreamerplayersession.o: In function `QGstreamerPlayerSession::QGstreamerPlayerSession(QObject*)':
qgstreamerplayersession.cpp:(.text+0xecc): undefined reference to `gst_video_connector_get_type'
.obj/qgstreamerplayersession.o: In function `QGstreamerPlayerSession::processBusMessage(QGstreamerMessage const&)':
qgstreamerplayersession.cpp:(.text+0x5b4c): undefined reference to `QGstUtils::gstTagListToMap(_GstStructure const*)'
collect2: error: ld returned 1 exit status
Makefile:129: recipe for target '../../../../plugins/mediaservice/libgstmediaplayer.so' failed
make[6]: *** [../../../../plugins/mediaservice/libgstmediaplayer.so] Error 1
Makefile:70: recipe for target 'sub-mediaplayer-make_first' failed
make[5]: *** [sub-mediaplayer-make_first] Error 2

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>