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Solves a set of linear equations. The input parameters "matrix1",
and "row_perm" come from luDecompostionD3x3 and do not change
here. The parameter "matrix2" is a set of column vectors assembled
into a 3x3 matrix of floating-point values. The procedure takes each
column of "matrix2" in turn and treats it as the right-hand side of the
matrix equation Ax = LUx = b. The solution vector replaces the
original column of the matrix.
If "matrix2" is the identity matrix, the procedure replaces its contents
with the inverse of the matrix from which "matrix1" was originally
derived.