x264enc: Consider subset relations of profiles when setting srcpad caps
x264enc: Consider subset relations of profiles when setting srcpad caps

constrained-baseline is a subset of baseline, is a subset of main,
is a subset of high profile.

https://bugzilla.gnome.org/show_bug.cgi?id=705425

GrokImageCompression/gst-plugins-ugly,jar1karp/gst-plugins-ugly,cablelabs/gst-plugins-ugly,StreamUtils/gst-plugins-ugly,jpakkane/gstreamer-plugins-ugly,reynaldo-samsung/gst-plugins-ugly,cablelabs/gst-plugins-ugly,GStreamer/gst-plugins-ugly,GrokImageCompression/gst-plugins-ugly,jpakkane/gstreamer-plugins-ugly,StreamUtils/gst-plugins-ugly,jar1karp/gst-plugins-ugly,shelsonjava/gst-plugins-ugly,krieger-od/gst-plugins-ugly,surround-io/gst-plugins-ugly,jpakkane/gstreamer-plugins-ugly,krieger-od/gst-plugins-ugly,sebras/gst-plugins-ugly,Kurento/gst-plugins-ugly,GrokImageCompression/gst-plugins-ugly,freedesktop-unofficial-mirror/gstreamer__gst-plugins-ugly,surround-io/gst-plugins-ugly,Kurento/gst-plugins-ugly,surround-io/gst-plugins-ugly,cablelabs/gst-plugins-ugly,Lachann/gst-plugins-ugly,jar1karp/gst-plugins-ugly,krieger-od/gst-plugins-ugly,krieger-od/gst-plugins-ugly,reynaldo-samsung/gst-plugins-ugly,reynaldo-samsung/gst-plugins-ugly,shelsonjava/gst-plugins-ugly,Kurento/gst-plugins-ugly,freedesktop-unofficial-mirror/gstreamer__gst-plugins-ugly,GStreamer/gst-plugins-ugly,shelsonjava/gst-plugins-ugly,sebras/gst-plugins-ugly,StreamUtils/gst-plugins-ugly,Lachann/gst-plugins-ugly,Lachann/gst-plugins-ugly,sebras/gst-plugins-ugly,freedesktop-unofficial-mirror/gstreamer__gst-plugins-ugly,GStreamer/gst-plugins-ugly