gstreamer-api: Add class for handling gst api versions through USE flag
gstreamer-api: Add class for handling gst api versions through USE flag

Adding new USE flags:
gstreamer_api: May be set to either 0.10 or 1.0.

When setting USE_gstreamer_api, the user may select whether he want to
use the new gst 1.0 api or the old 0.10 api. If 1.0 if chosen, then
packages not supporting the old 0.10 api is automatically not available.

Signed-off-by: Christian Sørensen <b4440a0607dba251e627cc55267a9b2ddd672a8a@prevas.dk>

oe-lite/multimedia,oe-lite/multimedia