gst-launch: print more errors to stderr and suppress more output in quiet mode
gst-launch: print more errors to stderr and suppress more output in quiet mode

If --quiet is given, don't print anything but errors. Also, make
sure errors are always printed to stderr and not to stdout.

Fixes #621595.

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