Better naming of utility test method
Don't use union

See
https://github.com/kripken/emscripten/wiki/CodeGuidelinesAndLimitations#code-that-might-be-useful-to-avoid
Note on another optimisation flag
Fix stupid error in benchmark
Rename 'convert' to 'render' (like snuownd)
DRY up benchmark code, add assertions to check for errors