Add sys_timeb header

- Remove incorrect header styles
- Use export.replace where header style was previously needed
- Check compilation of tests using system gcc

Based on what musl does.

wow i am stupid for writing this code

For some reason, C handles `==` before `&`.
So `a & b == c` is the same thing as `a & (b == c)`.

cbindgen can't handle negative numbers, see https://github.com/eqrion/cbindgen/issues/205