.SETITEM index array value

	command.  Changes the "index"th member of "array" to be "value",
	like SETITEM, but without checking for circularity.

	WARNING: Primitives whose names start with a period are DANGEROUS.
	Their use by non-experts is not recommended.  The use of .SETITEM
	can lead to circular arrays, which will get some Logo primitives into
	infinite loops.