Implement WASI Environment

[ErikMcClure]

inNative's default environment is the absolute bare minimum environment required to make WebAssembly work. While this ensures it can be ported to other platforms easily, until WebIDL bindings are standardized, it's extremely hard (if not sometimes impossible) to realistically interface with the host operating system, without relying on hacks that inNative provides for calling C functions.

A WASI environment should build on top of the default environment and properly implement all aspects of the WASI API for each platform that inNative supports (currently just Windows and POSIX). This would be a new project and a separate static library shipped with inNative that can be chosen when configuring an environment for compiling WebAssembly.