OpenGL 3.3 core profile does not support glBegin/glEnd/glVertex and related functions.
Replace all calls with VBOs & glDrawArrays/glDrawElements, or (preferably) with Gawain's immediate mode work-alike.
We must complete this task before switching to core profile.
The call for volunteers has more information about what needs to be done and how people can get involved.
We're tracking progress on this page, where you can browse files that need work and claim a piece of the action!