Merge cmake branch into master

[tromer]

We want to transition libsnark to CMake. The cmake branch mostly implements this, but its code lags a bit behind master.

We should finalize the CMake flags interface, and merge the cmake branch into master.

When finalizing the CMake flags, let's take the opportunity to remove all negations (e.g., NO_PT_COMPRESSION), and make sure all useful flags are expressed in a uniform way (currently some are Makefile proper flags and some are pass-through FEATUREFLAGS="-Dfoo".

[tromer]

Correction: the cmake branch has merged #45, which is a major refactoring of the algebra and FFT into separate libraries. Merging is now messier.

[chfast]

Can I help with this?

[tromer]

Tentative merged version (not yet tested): https://github.com/scipr-lab/libsnark/tree/cmake-master-merging

[copumpkin]

Isn't this done now?