Sets the eight bytes starting at the specified
byteOffset in this
object to the two's complement binary representation of the specified
value, which must fit in eight bytes.
In other words,
value must lie
between -263 and 263 - 1, inclusive.
Throws RangeError if
byteOffset is negative, or
byteOffset + 8 is greater than the length of this object.
void setInt64(int byteOffset, int value, [Endian endian = Endian.big]);