devel/hs-os-string: import hs-os-string-2.0.2.1

An implementation of platform specific short OsString, which is:

* on windows wide char bytes ([Word16])
* on unix char bytes ([Word8])

It captures the notion of syscall specific encoding (or the lack thereof)
to avoid roundtrip issues and memory fragmentation by using unpinned byte
arrays. Bytes are not touched or interpreted.

(pho)