buffer: Fix memory copying logic in copy_into()
buffer: Fix memory copying logic in copy_into()

https://bugzilla.gnome.org/show_bug.cgi?id=695035

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