qtdemux: Ensure that raw audio and video have properly aligned buffers
qtdemux: Ensure that raw audio and video have properly aligned buffers

That is, aligned to the basic type for audio and to 32 bytes for video.
Fixes crashes if the raw buffers are passed to SIMD processing functions.

https://bugzilla.gnome.org/show_bug.cgi?id=774428

pexip/gst-plugins-good,pexip/gst-plugins-good,GrokImageCompression/gst-plugins-good,StreamUtils/gst-plugins-good,hizukiayaka/gst-plugins-good,GrokImageCompression/gst-plugins-good,StreamUtils/gst-plugins-good,GStreamer/gst-plugins-good,StreamUtils/gst-plugins-good,GrokImageCompression/gst-plugins-good,stfl/gst-plugins-good,hizukiayaka/gst-plugins-good,GStreamer/gst-plugins-good,hizukiayaka/gst-plugins-good,GStreamer/gst-plugins-good,pexip/gst-plugins-good,stfl/gst-plugins-good,pexip/gst-plugins-good,stfl/gst-plugins-good,GrokImageCompression/gst-plugins-good,StreamUtils/gst-plugins-good,pexip/gst-plugins-good,GStreamer/gst-plugins-good,stfl/gst-plugins-good,hizukiayaka/gst-plugins-good