This adds code to translate the profile_and_level indication from the
MPEG-4 video (ISO/IEC 14496-2) headers to a string profile/level. The
mappings are taken from the spec and Wireshark's code, and might need to
be expanded on.
https://bugzilla.gnome.org/show_bug.cgi?id=617314
API: gst_codec_utils_mpeg4video_get_profile()
API: gst_codec_utils_mpeg4video_get_level()
API: gst_codec_utils_mpeg4video_caps_set_level_and_profile()