Some compile fixes and a DUB package description file

Mostly fixes some conflicting type definitions (happens only if multiple modules are imported at the same time) and relaxes some `version(Win32)` statements to `version(Windows)`, so that compiling with -m64 works on Windows.

I've also added a basic "package.json" so that the repository can be registered in the DUB package registry.

One general question for Deimos bindings: What is the policy for pre-compiled Windows binaries?

I usually always include binaries for Windows in my projects so that building doesn't involve compiling the C library and creating the proper import library for DMD (and often a bunch of fiddling around with make files). Is that something acceptable for Deimos libraries or should these repositories rather stay binary-free?