gstcheck: add docs for gst_check_setup_src_pad_by_name()
gstcheck: add docs for gst_check_setup_src_pad_by_name()

https://bugzilla.gnome.org/show_bug.cgi?id=734142

shelsonjava/gstreamer,shelsonjava/gstreamer,centricular/gstreamer,jpxiong/gstreamer,StreamUtils/gstreamer,shelsonjava/gstreamer,krichter722/gstreamer,mparis/gstreamer,jpxiong/gstreamer,mparis/gstreamer,StreamUtils/gstreamer,centricular/gstreamer,shelsonjava/gstreamer,mparis/gstreamer,krichter722/gstreamer,StreamUtils/gstreamer,mparis/gstreamer,centricular/gstreamer,StreamUtils/gstreamer,krichter722/gstreamer,centricular/gstreamer,mparis/gstreamer,StreamUtils/gstreamer,jpxiong/gstreamer,shelsonjava/gstreamer,krichter722/gstreamer,krichter722/gstreamer,centricular/gstreamer,jpxiong/gstreamer,jpxiong/gstreamer