IMAGE must be an image created with `create-image' or `defimage'.
IMAGE is displayed by putting an overlay into the current buffer with a
`before-string' STRING that has a `display' property whose value is the
-image. STRING is defaulted if you omit it.
-The overlay created will have the `put-image' property set to t.
+image. STRING defaults to \"x\" if it's nil or omitted.
+The overlay created by this function has the `put-image' property set to t.
POS may be an integer or marker.
AREA is where to display the image. AREA nil or omitted means
display it in the text area, a value of `left-margin' means