Original commit message from CVS:
* gst/videoscale/Makefile.am:
* gst/videoscale/gstvideoscale.c:
* gst/videoscale/gstvideoscale.h:
* gst/videoscale/vs_4tap.c:
* gst/videoscale/vs_4tap.h:
* gst/videoscale/vs_image.c:
* gst/videoscale/vs_image.h:
* gst/videoscale/vs_scanline.c:
* gst/videoscale/vs_scanline.h:
Add a 4-tap image scaler.  Theoretically looks much prettier.
The tap calculation could use some improvement.