word arrays B<r> and B<t>. B<n2> must be a power of 2. It computes
B<a>*B<b> and places the result in B<r>.
-bn_mul_part_recursive(B<r>, B<a>, B<b>, B<n>, B<tna>, B<tnb, B<tmp>)
+bn_mul_part_recursive(B<r>, B<a>, B<b>, B<n>, B<tna>, B<tnb>, B<tmp>)
operates on the word arrays B<a> and B<b> of length B<n>+B<tna> and
B<n>+B<tnb> and the 4*B<n> word arrays B<r> and B<tmp>.