Replace the type and function prefix to follow the conventions:
- Use `GST_TYPE_DC1394_SRC` instead of `GST_TYPE_DC1394`.
- Use `GstDC1394Src` and `GstDC1394SrcClass` instead of
`GstDc1394` and `GstDc1394Class`.
- Use `gst_dc1394_src` instead of `gst_dc1394`.
https://bugzilla.gnome.org/show_bug.cgi?id=763026