1) Document the behavior of "typeset -n existing_var" (via Jun T. comment)
2) Prohibit "typeset -nm pattern" because, well, it's insane. Add test.
3) Improve doc for ${(!)ref} including ${{t!)ref} (Jun T.)
4) Fix doc for how-to unset of a named ref (Jun T.)
5) Allow "typeset +r -n ref" and "typeset +r +n ref" (Jun T.)
6) Fix "typeset -r -n ref=param" to create readonly references
7) Avoid accidental removal of PM_UNSET flag (Jun T.) and update test
8) Fix "typeset -gn ref=value" and add a test for it
9) Add tests for read-only reference behavior
10) Fix infinite recursion when resolving scope of an unset local
named reference, add test.