owr_payload: enable GL only for apple h264 encoders
owr_payload: enable GL only for apple h264 encoders

Restrict GLMemory to the apple H264 encoders only. Other encoders don't support
GLMemory (yet) so fallback to downloading to sysmem for those.

shoreflyer/openwebrtc,pererikb/openwebrtc,stefhak/openwebrtc,shoreflyer/openwebrtc,pererikb/openwebrtc,multipath-rtp/openwebrtc,EricssonResearch/openwebrtc,multipath-rtp/openwebrtc,alessandrod/openwebrtc,multipath-rtp/openwebrtc,EricssonResearch/openwebrtc,shoreflyer/openwebrtc,EricssonResearch/openwebrtc,pererikb/openwebrtc,alessandrod/openwebrtc,philn/openwebrtc,pererikb/openwebrtc,multipath-rtp/openwebrtc,shoreflyer/openwebrtc,philn/openwebrtc,philn/openwebrtc,alessandrod/openwebrtc,philn/openwebrtc,EricssonResearch/openwebrtc,multipath-rtp/openwebrtc,multipath-rtp/openwebrtc,alessandrod/openwebrtc,philn/openwebrtc,stefhak/openwebrtc,stefhak/openwebrtc,EricssonResearch/openwebrtc,philn/openwebrtc,stefhak/openwebrtc,stefhak/openwebrtc,alessandrod/openwebrtc,EricssonResearch/openwebrtc,shoreflyer/openwebrtc,multipath-rtp/openwebrtc,shoreflyer/openwebrtc,pererikb/openwebrtc,shoreflyer/openwebrtc,stefhak/openwebrtc,EricssonResearch/openwebrtc,alessandrod/openwebrtc,pererikb/openwebrtc,pererikb/openwebrtc,philn/openwebrtc