add method to check whether DRC_BASE is defined
add method to check whether DRC_BASE is defined

manuelli/director,mitdrc/director,patmarion/director,openhumanoids/director,manuelli/director,patmarion/director,manuelli/director,mitdrc/director,openhumanoids/director,openhumanoids/director,patmarion/director,patmarion/director,manuelli/director,patmarion/director,openhumanoids/director,mitdrc/director,openhumanoids/director,mitdrc/director,mitdrc/director,manuelli/director