The nodes now have more control over how their accelerated shaders/sample
functions are run, as well as how items are popped off the value tables.
This allows for various optimizations that we didn't have access to before.
Results are identical (tested with Olive 0.1.x). Using a straight multiply is faster if the compiler doesn't optimize pow(). It's also safer because with pow(), [the result is undefined if x<0 or if x=0 and y≤0](https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/pow.xhtml).
itsmattkc