Gets the list of children on this.
The list is exactly the list of strings for which it is not an error to call get_child.
There is little reason to call this function from "normal" code, since you should already know what children are in your schema. This function may still be useful there for introspection reasons, however.
You should free the return value with strfreev when you are done with it.
a Settings object
a list of the children on this