Milestone: Run tiny-keccak tests

[eira-fransham]

This will be a great exercise of our codegen, since tiny-keccak has long stack arrays and ugly unrolled loops that are much more similar to real-world code compared to the tiny loops we've been working with thus far.

• i32.store/i32.load
• Data section
• 64-bit equivalents to all 32-bit instructions - we already treat all values as 64-bit when their size is unknown so this is mostly a case of adding the i64.xxxx instructions and changing the Immediate representation, which shouldn't be difficult.
• Multiple returns - I'm not certain that this is necessary but I would be surprised if there isn't somewhere that uses this to (for example) return a struct. Of course, it's possible that LLVM always compiles to use a hidden argument, I remember me and @pepyakin looking at this and that appeared to be how it was compiling it.

[sunfishcode]

Cool, this sounds like a great milestone.

I posted a comment about i32.load/i32.store in CraneStation/lightbeam#13.

[alexcrichton]

Lightbeam was removed in #3390 as explained in RFC 14, so I'm going to close this.