[ENHANCEMENT] Add #define guards to run_dynamics_fast

### Relation

The MATLAB mex function, [`run_dynamics_fast`](https://github.com/Airspace-Encounter-Models/em-core/blob/master/matlab/utilities-1stparty/runDynamicsFast/run_dynamics_fast.c) is used by multiple repositories, including `em-model-manned-bayes` to simulate aircraft trajectories with a 6DOF physics model. There are various `#define` statements that are unguarded.

### Description

Add [`#define` guards](https://google.github.io/styleguide/cppguide.html#The__define_Guard) to prevent multiple inclusions.

### Alternatives

`#define` guards are a good best practice and should be implemented.

### Additional

Recommend addressing issue #10 for the use `const` variables before addressing this issue.

While the contributing guidelines does not define a style guide for C++, we currently recommend the [Google C++ Style Guide](https://google.github.io/styleguide/cppguide.html) for this issue.