Add test for ucontext.h.  (Needed for cothreads.c)
Add test for ucontext.h.  (Needed for cothreads.c)

Original commit message from CVS:
Add test for ucontext.h.  (Needed for cothreads.c)

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