o new function random_sat
 o new example in tiling.ml (tiling the 8x8 chessboard with 2x1 dominoes *)
 o init removed and subsumed by set_max_var
 o improved efficiency (one node table for each variable)

July 16, 2009 (version 0.2)
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 o fixed bug in count_sat (unused variables below the top variable where not
   taken into account)

June 7, 2008 (version 0.1)
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 o LGPL license, with special exception for linking (see LICENSE)