gstvalue: make new gst_value_list_merge() work properly
gstvalue: make new gst_value_list_merge() work properly

Fix freeing of partially-inited list value when both values
passed are equal and we want to return a single non-list
value as result. Fixes unit test. Also fix up docs a bit.

https://bugzilla.gnome.org/show_bug.cgi?id=637776

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