Add all the remaining #define macros from predicates.c

[DanielVandH]

The remaining arithmetic functions still need to be added but here I've added all the remaining #define macros.

• To test them all properly, I rewrote the #define macros as functions in C so that we can get them through @ccall. I tested my conversions in C in macro_defs.c. I've pretty much never used C (only one other time for ~20 minutes before looking into this PR) so my C code is probably very rough.
• I then test the Julia versions by comparing to the @ccall. For some reason the only one not exactly correct all the time is Two_Square. I don't know why exactly...

I restructured the code a bit to help organise it better when I later add the remaining functions.

(The point here being of course that I'm trying to get all the macros/arithmetic functions in and tested so I can port over the remaining predicates)

[DanielVandH]

For some reason the only one not exactly correct all the time is Two_Square. I don't know why exactly...

Could be related to this comment

/* An expansion of length two can be squared more quickly than finding the /
/ product of two different expansions of length two, and the result is /
/ guaranteed to have no more than six (rather than eight) components. */

in the code. Maybe my tests are breaking the expansion of length two assumption.

[DanielVandH]

Actually, Two_Square isn't even used anywhere in predicates.c.. I'll just remove it. This is good to go.

[DanielVandH]

Actually, Two_Square isn't even used anywhere in predicates.c.. I'll just remove it. This is good to go.

Fixed! #12 - it was a bug in the original code.