manual: improve clock docs a little
manual: improve clock docs a little

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