Types that aren't used to generate code are pruned away. Try using your type in a function declaration.
You'll need to include headers to use functions from external libraries.
When the translator can't handle a translating a function for some reason it omits the implementation and prints the reason. This is configurable and visible when you're running the tool locally. Currently this web interface doesn't show warning messages generated during translation.
We've captured many of the features we don't support on the Known Limitations of Translation wiki page.