* doc/lispref/text.texi (Special Properties): Describe the new
'inhibit-read-only' text property. Add cross-reference to where
read-only buffers are described.
* doc/lispref/buffers.texi (Read Only Buffers): Mention that
'inhibit-read-only' property exempts text from being read-only.
Add cross-reference to "Special Properties".
* etc/NEWS: Move the entry about 'inhibit-read-only' property to
its place and mark it documented.