Imagick::spreadImage needs to allow PixelInterpolateMethod to be set.

[Danack]

#if MagickLibVersion >= 0x700
	{
	//TODO allow PixelInterpolateMethod be set
	PixelInterpolateMethod method = BilinearInterpolatePixel;
	status = MagickSpreadImage(intern->magick_wand, radius, method);
	}
#else
	status = MagickSpreadImage(intern->magick_wand, radius);
#endif