plugin: add since: tags for the api docs.
plugin: add since: tags for the api docs.

The previous related commit added new API.
API: add gst_plugin_get_cache_data, gst_plugin_set_cache_data

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