Prot# D9770C00012: A Randomised, Double-Blind, Multicentre Dose-Finding Phase IIb Study for up to 8wks' Treatment w/AZD0865 25,50,75mg & Esomeprazole 40mg, Given Orally 1x Daily for the Healing of Erosive Esophagitis in Adult Subjects w/GERD w/Erosive Eso