Special handling of negative numbers in the writeBin() method implementation.

JS numbers are double-precision floating points (doubles) and doubles cannot
be converted to unsigned integers uniformly across all architectures (e.g.
specifically on ARM, negative numbers would mostly get converted to 0U).

For details, see
https://www.embeddeduse.com/2013/08/25/casting-a-negative-float-to-an-unsigned-int/