Re: "until" facility in RobotC?
In response to your first point: No, the until functions are in fact provided by the inclusion of procedures calling the while facility. ROBOTC doesn't support "until" and unfortunately we don't plan on implementing it any time soon. Though as you can see with the Natural Language Library, you can get around this with some very simple programming.
Which brings us to point 2: Yes! You can create as many custom libraries as you like. Just put them somewhere and include a " #include "path/morepath/file.extension" " command at the top of your code. It works the same in the H99 framework as regular ROBOTC since it's the same general ROBOTC compiler. However, some very advanced, robot-specific commands won't work in the Virtual World. Things like the VEX LCD screen or some pwm regulation code. But it sounds to me like for your class you don't need things that advanced and in fact, want to create your own more simple library--which is perfectly OK!
If you make some awesome libraries, feel free to share it with the rest of the ROBOTC community