Add timing for computing the Mandelbulb itself.
Break up Mandelbulb worklet code to match mathematical description

This devides the worklet into two functions. This might make things a
tad bit slower if the compiler does not unroll the inlines as well, but
I've also removed a square root, which speeds things up at least as well
as where we started.
Skip computation of 0 iteration of Mandelbulb

It is trivially the input coordinate
Return MAX_ITERATION for Mandelbulb positions that don't escape

It's more correct and it removes an inner surface that you can't see,
shouldn't be there, and slows down the rendering.
Fix bounds of data and FPS calculation

The bounds of the data extended beyond the bounds of the Mandelbulb, so
did not produce anything interesting. Shrink the bounds to provide more
detail in the Mandelbulb surface.

The frame-per-second report was only supposed to update if the FPS
changed by more than 1, but the previous FPS being compared to was never
updated properly.
Add Mandelbulb command line option for adjusting size of grid
Cosmetic changes
Merge branch 'mandlebulb-changes'