HISTORY of blur:
   2.1 - 11 Sep 1998 Miles O'Neal (meo@rru.com)
     - fixed blur_prepare_row() to handle lower bound properly
     - fixed bug involving INTERACTIVE vs NON-INTERACTIVE
     - fixed several bugs introduced when alpha support added
     - added several optimizations
     - upgraded explanation of algorithms
   2.0 -  1 May 1998 Miles O'Neal (meo@rru.com)
     - based on randomize 1.7
   1.X - maintained by others who left little trail
