(list-character-sets): Completely

(list-character-sets): Completely
rewritten.
(sort-listed-character-sets): New function.
(list-character-sets-1): Completely rewritten.
(list-character-sets-2): New function.
(non-iso-charset-alist): New variable.
(decode-codepage-char): New function.
(charset-history): New variable.
(read-charset) (list-block-of-chars)
(list-iso-charset-chars)
(list-non-iso-charset-chars)
(list-charset-chars): New functions.
(mule-diag): Call list-character-sets-2, not
list-character-sets-2.
(dump-charsets): Likewise.