Fix AMRWBEnc overflow

            for (i = 0; i < L_SUBFR; i++)

            {

                L_tmp = (code2[i] * gain_code)<<1;

                L_tmp = (L_tmp << 5);

                L_tmp += (exc2[i] * gain_pit)<<1;

                L_tmp = (L_tmp << 1);

                L_tmp = L_mult(code2[i], gain_code);

                L_tmp = L_shl(L_tmp, 5);

                L_tmp = L_add(L_tmp, L_mult(exc2[i], gain_pit));

                L_tmp = L_shl(L_tmp, 1);

                exc2[i] = voround(L_tmp);

            }