memory: add API for handling memory blocks
memory: add API for handling memory blocks

Adds some API to handle memory blocks.

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