v20180710

1. Reorganised all include files so each may be included by itself.
2. Reorganised management of precision to use bit precision, not decimal.
3. Made various adjustments so tests pass with clang as well as gcc, both with multiprecision floating point and without.
4. Added some functions for listing binary cubics up to GL(2,Z)-equivalence.
5. Fixed some issues caused by using #define instead of #typedef in handling types.