A Six-Week, Randomized, Double-Blind, Parallel Group Extension Study To Evaluate The Long-Term Safety, Tolerability, And Efficacy Of Low And High Doses Of Bl-1020 Compared To Risperidone, In Schizophrenic Patients Previously Treated In Study Bl-1020 Iib For A Maximum Of Six Weeks With Bl-1020 (High Dose, Low Dose), Risperidone Or Placebo