flush() after the type builtin prints its output.

Without this change, debootstrap stops with an error.  With this change,
it completes successfully and I'm able to chroot into the result and run
commands!

Addresses issue #62.

core/builtin.py

@@ -964,6 +964,9 @@ def Type(argv, funcs, path_val):
          # bash prints the function body, busybox ash doesn't.
          pass

  # REQUIRED because of Python's buffering.  A command sub may give the wrong
  # result otherwise.
  sys.stdout.flush()
  return status