Better test file. Uses presets.
Fix mouse drawing bug.
Experimenting with fftw threads.

* Disabled for now, they require adding thread support to the fftw build
in naclports.

* Also added FPS display to test/index.html -- I didn't notice any
speed improvements with threads, but it looked like all my CPUs threads
were busy already; I'll revisit this after the refactor.
Simplify the code a lot.

* Remove GPU version
* Remove all extra threads
* Remove buffer saving, pausing, rendering smoother/kernel, etc.
* Use NaCl SDK build system
* Use ppapi_simple with ps_context_2d for rendering