LXARC(ixc.i2.r, iyc.i2.r, radius.i2.r, start.i2.r, count.i2.r
	      [,color.i2.r] [,filled.i1.r])

	This routine will draw an arc of a circle centered at (IXC,IYC)
	with radius RADIUS, on the LX color graphics display window.

	IXC,IYC	coordinates of the centerpoint

	RADIUS	radius of arc in pixels

	START	starting position of arc counted in pixels
		counterclockwise from the plus X direction.

	COUNT 	length of arc in pixels, counted
		counterclockwise from start

	COLOR	arc color

	FILLED	filled arc when TRUE

	See the descriptions of the LXPNT and LXMODE routines for information
	on color codes.  Arc pattern is	determined by the most recent call to
	LXPATT.  A pixel count can be generated from an angle THETA (in
	degrees) as follows:
		quads  = INT ((theta + 45.) / 90.)
		pixels = INT ((quads*1.41421 +
			 SIN (1.5708*(theta/90. - quads)))*radius)