Remove unused fcmp GPL2 code

[ToddFincannon]

At one time, we used the fcmp library to get high-precision floating-point comparisons. We ended up not using it. This is a GPL v2 library incompatible with the MIT license, so we should remove it. This would require changing the sde.h header to remove the unused fcmp option.

[ToddFincannon]

I went ahead and replaced the macros that served as a shim for fcmp macros everywhere they occurred in the C code. They were all simple, and they only occurred in a few places. So fgt(a, b) is now a > b etc., which seems like an improvement.