fix for building on Raspberry Pi
Merge pull request #4 from ukscone/master

Fix for building on Raspberry Pi.
Refactored functions involving digits.
Initialize cofactor in the twist.
New benchmarks for new functions.
Prototypes for new utility functions.
Add tests for point at infinity.
Make tests more comprehensive.
Small adjustments in tests.
Add preset for supersingular curves.
Restore workint version of pp_dbl_k2_projc_lazyr().