unicode jit emchars broken

[Ilya N. Golubev]

After changes from 2006-11-02 to 2006-11-07, including that of `src'
of 2006-11-05, when trying to convert previously unknown unicode code
point 0x10db to `jit-ucs-charset-0' emchar, xemacs signals the
following error.

(invalid-argument "Invalid value for `ccl-program'" ccl-encode-to-ucs-2)

In the following bt.

#3  0x080db30a in Fsignal (error_symbol=137497924, data=144901376)
    at src/eval.c:2304
#4  0x080db61b in signal_error_1 (sig=137497924, data=144901376)
    at src/eval.c:2420
#5  0x080db83e in signal_error (type=137497924, 
    reason=0x82bb700 "Invalid value for `ccl-program'", frob=137696300)
    at src/eval.c:2531
#6  0x080dbe39 in invalid_argument (
    reason=0x82bb700 "Invalid value for `ccl-program'", frob=137696300)
    at src/eval.c:2887
#7  0x081ad471 in Fmake_charset (name=144617124, doc_string=139233356, 
    props=144901352)
    at src/mule-charset.c:595
#8  0x08235057 in unicode_to_ichar (code=4315, charsets=0x8364970)
    at src/unicode.c:1141
#9  0x08236329 in decode_unicode_char (ch=4315, dst=0x8a30e98, data=0x8a30cd0, 
    ignore_bom=0) at src/unicode.c:1712

This happens both before and after dumping, if ucs -> emchar mapping
for the ucs code point in question was not set before.  The test case
is `decode-coding-region utf-8' of text containing the representation
of this character.

Please fix.