Multiple source file support

[eholk]

How do we want these to work? One Rust module per Wasm module? One Wasm module per crate? How do we decide what is exported to Wasm?

[eddyb]

I believe multiple files are already supported, and if you follow the LLVM model, you will want one wasm module per crate.
The relevant part of deciding what's exported from current LLVM trans is mostly using information already computed in the compiler, and filtering out some cases which are never exported.

[eholk]

#32 shows we have support for this (although multiple crates are probably a different issue), so I'm going to go ahead and close this.