Documentation of characters in the user's manual is out-dated

In https://cmucl.org/docs/cmu-user/html/Characters.html#Characters, cmucl's characters are described. This is out-of-date since cmucl now supports unicode. Characters are 16-bits long, corresponding to utf-16 code-units.

The set of recognized characters is far larger than is listed in the table. In fact, cmucl recognizes any unicode character name. And also supports hex names (#\+xxxx) for characters.

Update the manual, possibly just pointing to the internationalization section for more details?