New stuff & fixes in Blender OSA filtering.

While investigating alternative filters (Mitchell), I found two small
errors in the Gauss code, it clipped wrong and multiplied wrong, causing
settings other than filter size 1.0 to not work properly.

Took the last-minute liberty to add more filter types in Blender too.
Also wrote an extensive log about how sampling & filtering in Blender
works.

http://www.blender3d.org/cms/Samples_and_Filtering.723.0.html

source/blender/src/transform_generics.c

@@ -74,6 +74,7 @@
 #include "BKE_utildefines.h"
 
 #include "BSE_view.h"
+#include "BDR_unwrapper.h"
 
 #include "BLI_arithb.h"
 #include "BLI_blenlib.h"