made readut self-contained.

modules/base/header.lua

@@ -119,7 +119,7 @@ do -- so local works
   end
   return false
  end
- function os.readut()
+ local function readut()
   local f=fs.open("/boot/sys/users.dat","rb")
   if not f then return false end
   local C=fs.readall(f)
@@ -187,5 +187,5 @@ do -- so local works
   end
   return false
  end
- spawn("read users",os.readut)
+ spawn("read users",readut)
 end