Compiled block optimizations

[cpdt]

At the moment, performance for audio generation in Axiom can be quite poor. Here are a few potential optimization-related tasks I've identified:

• [ ] Add per-node profiling
• [x] Pass num values by value to avoid allocas in node functions
• [x] Use SSE and disable denormals with it
• [x] Use fastcc for functions internally (not sure if this would make much of a difference, but it's a pretty simple change so probably worth it)
• [ ] Look at why the reverb module uses so much time, and what can be done to improve it (I think this is related to the delay function being slow)
• [x] Use tables for oscillators (and sin/cos in general?)
• [ ] Optimize note function
• [ ] Optimize biquad filters and delay function (why is delay so slow at the moment?)
• [ ] Optimize the graph control (it's not too bad CPU wise, but we can expect to have a lot active at any moment in time and it should be possible to optimize a lot from the current implementation)

[cpdt]

I'm going to close this since #151 (SSE and other perf improvements) has been merged. That PR doesn't cover the function optimizations mentioned above, I'm not sure if they're necessary at this point so we can re-open if we decide they need improving.