WRHI001-GATES- A Randomized, Double-Blind, Multi-Centre, Parallel-Group Phase 3b Study To Demonstrate Non-Inferiority Of Stavudine (20 Mg Twice Daily) Compared With Tenofovir Disoproxil Fumarate (300 Mg Once Daily) When Administered In Combination With Lamivudine And Efavirenz In Anti Retroviral-Naive Patients Infected With HIV-1