It should be great to add the folowing functions to PR and piston joints:
dJointAddPRForce (add PR torque already exists),
dJointPistonAddTorque (add Piston force already exists)
Because these functions are useful and already implemented for otherjoints.
Th !
Moved to http://bitbucket.org/odedevs/ode/issue/14/djointaddprforce-and-djointpistonaddtorque