Replace precomputed matrix with operation-vector

 - The precomputed matrix was created from the operation vector.
 - The operation vector scale much better with problem size than matrix
   multiplication.
 - Storing an operation vector for block size 347 takes less than half of the
   space of storing a precomputed matrix.
 - Creating encoded symbols for block size 347 is 100x faster with an
   operations vector using SSSE3 than using a precomputed matrix. Note that
   other parts also take time so the overall performance increase is around 40x
   for block size 347.
 - The performance gains also apply to decoding.

Signed-off-by: Anders Martinsson <anders.martinsson@intinor.se>