spritestitch_specialmargins
[OBSOLETE]
Almoast the same as uiz_back_spritestitch, but this allows you to have corners that are of different size than only the given margins that are needed for the other spritestitch functions.
The edges must still be as wide as the margins and the rest of your border.
You will need to define the size of your corners. You can do this by going into your sprite, pressing "Modify Mask" and click "Manual" on the Bounding Box.
Now browse to image 6 which should be the bottom-right corner, put on the top right of your sprite.
Leave the Left and Top values to 0 but change the Right and Bottom values is such a way that The bounding box is inside the corner,
but not on the border of the corner itself. Like this:
