Radiation Therapy With or Without Chemotherapy in Treating Patients With Advanced Head and Neck Cancer

head and neck cancer, stage ii squamous cell carcinoma of the lip and oral cavity, stage ii verrucous carcinoma of the oral cavity, stage iii squamous cell carcinoma of the lip and oral cavity, stage iii verrucous carcinoma of the oral cavity, stage iv squamous cell carcinoma of the lip and oral cavity, stage iv verrucous carcinoma of the oral cavity, stage ii squamous cell carcinoma of the oropharynx, stage iii squamous cell carcinoma of the oropharynx, stage iv squamous cell carcinoma of the oropharynx, stage ii squamous cell carcinoma of the nasopharynx, stage iii squamous cell carcinoma of the nasopharynx