#13 Rewrite in ANSI C

With the goal of targeting minimal platforms, rewriting in ANSI C would be desirable: - Set `-std=c11` in compile flags - Rewrite or eliminate GNU extensions: `strdup`, `fmemopen`, etc. - Verify dependencies, both embedded and dynamically linked (LMDB may not be ANSI C, so the target systems would have to be able to support installing it separately)