format: use GST_FORMAT_UNDEFINED and few casts to GstFormat
format: use GST_FORMAT_UNDEFINED and few casts to GstFormat

Fixes warning #188: enumerated type mixed with another type reported by ICC.

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