Pointers, vectors, and doubling.

Pointers, vectors, and doubling.

Use pointers for field element constants and simplify scalarbase copy setup. Implement point doubling function. Vectorize selection logic and use built-in for swapping bits. Tweak error handling, maybe fix liftString at some point. Use immediate offsets instead of pointer arithmetic where possible. Pass pointers directly to scalarmult, add, and cswap.