(utf-16-decode-ucs): Handle a surrogate

(utf-16-decode-ucs): Handle a surrogate
pair correctly.  Call ccl-mule-utf-untrans for untranslable chars.
(utf-16le-decode-loop): Set r5 to -1 before loop.
(utf-16be-decode-loop): Likewise.
(ccl-decode-mule-utf-16le): Add EOF processing block.
(ccl-decode-mule-utf-16be): Likewise.
(ccl-decode-mule-utf-16le-with-signature): Likewise.
(ccl-decode-mule-utf-16be-with-signature): Likewise.
(ccl-decode-mule-utf-16): Likewise.  Set r5 to -1 initially.
(ccl-mule-utf-16-encode-untrans): New CCL.
(utf-16-decode-to-ucs): Handle pre-read character.
(utf-16le-encode-loop): Handle surrogate pair.
(utf-16be-encode-loop): Likewise.
(ccl-encode-mule-utf-16le-with-signature): Adjusted for the change
of utf-16le-encode-loop.
(ccl-encode-mule-utf-16be-with-signature): Adjusted for the change
of utf-16be-encode-loop.
(mule-utf-16-post-read-conversion): Call
utf-8-post-read-conversion at first.
(mule-utf-16[{le|be}], mule-utf-16{le|be}-with-signature): Include
CJK charsets in safe-charsets if utf-translate-cjk-mode is on.
Add post-read-conversion and pre-write-conversion.