basesink: lower GST_BASE_SRC_FLAG_LAST
basesink: lower GST_BASE_SRC_FLAG_LAST

It wouldn't leave that much room for subclass users

ensonic/gstreamer,surround-io/gstreamer,lubosz/gstreamer,cfoch/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,krieger-od/gstreamer,justinjoy/gstreamer,collects/gstreamer,justinjoy/gstreamer,jpxiong/gstreamer,jpakkane/gstreamer,jpakkane/gstreamer,centricular/gstreamer,cablelabs/gstreamer,StreamUtils/gstreamer,cablelabs/gstreamer,jpakkane/gstreamer,centricular/gstreamer,collects/gstreamer,shelsonjava/gstreamer,ensonic/gstreamer,shelsonjava/gstreamer,jpxiong/gstreamer,cfoch/gstreamer,krichter722/gstreamer,Lachann/gstreamer,jpxiong/gstreamer,surround-io/gstreamer,surround-io/gstreamer,mparis/gstreamer,surround-io/gstreamer,krichter722/gstreamer,collects/gstreamer,krichter722/gstreamer,cablelabs/gstreamer,krieger-od/gstreamer,cablelabs/gstreamer,centricular/gstreamer,ensonic/gstreamer,centricular/gstreamer,StreamUtils/gstreamer,cfoch/gstreamer,justinjoy/gstreamer,lovebug356/gstreamer,Lachann/gstreamer,justinjoy/gstreamer,jpxiong/gstreamer,lubosz/gstreamer,StreamUtils/gstreamer,collects/gstreamer,mparis/gstreamer,krieger-od/gstreamer,lovebug356/gstreamer,lubosz/gstreamer,collects/gstreamer,shelsonjava/gstreamer,mparis/gstreamer,ensonic/gstreamer,mparis/gstreamer,mparis/gstreamer,lubosz/gstreamer,krichter722/gstreamer,surround-io/gstreamer,shelsonjava/gstreamer,ensonic/gstreamer,Lachann/gstreamer,lovebug356/gstreamer,krieger-od/gstreamer,cablelabs/gstreamer,cfoch/gstreamer,jpakkane/gstreamer,lovebug356/gstreamer,jpxiong/gstreamer,lubosz/gstreamer,Lachann/gstreamer,jpakkane/gstreamer,centricular/gstreamer,shelsonjava/gstreamer,cfoch/gstreamer,Lachann/gstreamer,lovebug356/gstreamer,krieger-od/gstreamer,justinjoy/gstreamer,krichter722/gstreamer