Add sys_timeb header

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

Doesn't link yet due to "multiple definitions of malloc", because some are supplied by some library of bash itself. Really odd.

I really really wish I could actually test this on redox. All I know is: it compiles