made libmtar cope with lower memory systems at the expense of speed

lib/libmtar.lua

@@ -43,7 +43,9 @@ function mtar.iter(stream) -- table -- function -- Given buffer *stream*, return
   return rb
  end
  return function()
-  stream:read(remain)
+  while remain > 0 do
+   remain=remain-#stream:read(math.min(remain,2048))
+  end
   local nlen = toint(stream:read(2) or "\0\0")
   if nlen == 0 then
    return