Allow to compile on Windows

[Temtaime]

Hello. Your versions of bsdiff is great with improvements to an original algorithm, and i want to use it on windows too. It'd be great if some linux specific headers were removed and tool were compatible with MSVC. Thanks for understanding.

[bryteise]

This seems unlikely to be something we'd work on I'm sorry.

[phmccarty]

This type of change is not something I can commit to work on myself. But I will consider any PRs that enable builds on different platforms or otherwise improve cross-platform compatibility.