new qcam discoveries

I grafted Thomas Davis' bidirectional code into my xfqcam and did some
experimenting.  I've learned a couple cool things:
 1. Initially I couldn't get the image to update so I added one more
 out(0x26), inw, handshake, inw after reading the picture and that seems
to do the trick.  Now, only the send xfermode command has to be in the
loop.  As a result, it's really fast, my framerate has doubled.  On smaller 
images I'm getting 24 fps- so apparently the camera has some bandwidth to
spare (unless I'm toasting it! :^) )

2. zoom modes- I can get images of any arbitrary width and height by using
the image size commands.  The xfermode used determines zoom.  So if
I request a 80x60 image in 320x240 mode I get a closeup, in 160x120 it's 
a little less close and of course 80x60 mode gives a normal image.  So
there's actually up to 2 levels of zoom- it's been a while since I've
used Windows but if I remember right the Connectix programs only support 1.