Fix bug where cmucl was no longer recognizing things like

#\latin_small_letter_a.  This failure is caused by the new
SEARCH-DICTIONARY function that does partial completion, and
UNICODE-NAME-TO-CODEPOINT function wan't aware of the new way.

We could change UNICODE-NAME-TO-CODEPOINT to do the appropriate thing
with the new way, but I (rtoy) decided it would be nice to have the
old function around too.  Hence, restore the old version and use it.