fix a bug in Lwt_io.read_all
fix a bug in Lwt_io.read_all

Ignore-this: 53a774068cd56865e979894515e71759

darcs-hash:20090518192120-c41ad-741d869c29764303c86f26f46f63c28548c33ea9

janestreet/lwt-async,ocsigen/lwt,c-cube/lwt,ocsigen/lwt,gfxmonk/lwt,fdopen/lwt,fdopen/lwt,ocsigen/lwt,rgrinberg/lwt,rneswold/lwt,rneswold/lwt,rneswold/lwt,gfxmonk/lwt,mfp/lwt,mirage/lwt,mfp/lwt,rgrinberg/lwt,c-cube/lwt,rgrinberg/lwt,rgrinberg/lwt,c-cube/lwt,mirage/lwt,janestreet/lwt-async