( resource image [, int interlace] )
imageinterlace() turns the interlace bit on or off.
If interlace is 1 the image will be interlaced, and if interlace
is 0 the interlace bit is turned off.
If the interlace bit is set and the image is used as a JPEG image,
the image is created as a progressive JPEG.
This function returns whether the interlace bit is set for the