What's supported:
* #include directives, e.g. '#include "data/scripts/foobar.c"' (like before, but less buggy)
* simple #define directives, e.g. '#define MYNUMBER 7' or '#define my_xdir getentityproperty(self, "xdir")'
What's not supported (yet):
* Function-style defines, e.g. '#define rem(x,y) (x % y)'
* Conditional directives (#if, #ifdef, #ifndef, #elif, #else, #endif)
* Any other C preprocessor directives such as #pragma, #warning, #error, etc.
