pisces, produceFillAlphas

[Johan Vos]

After spending lots of time optimizing JavaFX on iOS, I am now at the point
where scrolling is 10 times faster on iOS than on Android.
The scrolling in the iOS version of the Gluon JavaOne mobile schedule
builder is pretty good imho. On Android, it is much slower. I profiled and
compared both, and it turns out that on Android, we spend lots of time in
the native implementation of NativePiscesRasterizer.produceFillAlphas
(implemented in native-prism/NativePiscesRasterizer.c)

On average, calling this native function on an iPhone 6 takes 40,000ns
whereas on a Nexus 6, this takes about 800,000ns.

If anyone has a suggestion on how to improve or avoid this, I'm all ears.

Thanks,

- Johan