Input and output in [0, 4*n)

x += y*b. Assumes y >= 0 and that 0 <= b < NTL_SP_BOUND. Caller must assure that x does not exceed sz+2 limbs. x remains unnormalized.

j in [0, 2^{level-1}) a = b*2^{j*r*2^{l-level}}

blend even/odd slot-pairs 01234567, 89abcdef -> 01ab45ef

this assumes n is a multiple of 16

* @brief Displays Menu. * * @param None. * * @return None. ******************************************************************************/