BlackRockIO float multiplication is not precise

[muellerbjoern]

When analog input signals (channels > 128) are loaded the gain value is a float number by that the integer signal values are multiplied. This multiplication is done in different ways in the old BlackrockIO_v4 and the new BlackRockIO (happening in BaseRawIO, ll. 490 ff.). Both differ from the expected value. The behavior of the old IO can be explained because of the float precision loss whereas I could not reproduce the result of the new IO by trying to multiply manually at different precisions. The differences are at about the seventh significant digit, thus not extreme.