Frame stats

[VyrCossont]

All native runtimes now log frame durations and print a brief histogram to the console on a successful exit. This is intended for investigating #554 more easily than by eye, and doesn't need to be merged, although I've written it so that it could be.

$ wasm4 cart.wasm
Frame stats:
    0 ms:        1
    1 ms:        1
   14 ms:        1
   15 ms:       45
   16 ms:       45
   22 ms:        1
   33 ms:       53
   60 ms:        2
   78 ms:        1
>= 99 ms:        1

$ wasm4_glfw cart.wasm
Frame stats:
   16 ms:       58
   17 ms:       64
   29 ms:        1
   70 ms:        1
   96 ms:        1
>= 99 ms:        0