dentity: remove prepare_output_buffer
dentity: remove prepare_output_buffer

Correctly mark passthrough on the baseclass so that it can correctly do the
allocation of the output buffers.
Remove our custom prepare_output_buffer function now that the baseclass is
smarter.

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