Convert to new override syntax

This is the result of automated script conversion:

oe-core/scripts/contrib/convert-overrides.py .

converting the metadata to use ":" as the override character instead of "_".

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>

recipes-core/images/rpi-basic-image.bb

@@ -10,6 +10,6 @@ SPLASH = "psplash-raspberrypi"
 
 IMAGE_FEATURES += "ssh-server-dropbear splash"
 
-do_image_prepend() {
+do_image:prepend() {
     bb.warn("The image 'rpi-basic-image' is deprecated, please use 'core-image-base' instead")
 }