Issue #21383: OS X installer builds now use "make touch".
Issue 21554:  Repair an out-of-date tutorial example to reflect changes in shutil.
Issue 21198: Minor tarfile documentation bug.
Issue 21479: Fix markup for the TarFile.open() classmethod.
Issue #21545: Add .pop example and tweak comment about pure mutation methods.
Patch prepared by David Harrigan.