Fix copy-char-table on syntax tables

[Stephen J. Turnbull]

COMMIT 21.5

Per Olivier's request.

I'm curious: Why does this fix the problem?  It's "obviously correct,"
but I would think this would be a lazy equivalent of an explicit copy.
Was the wrong thing getting copied, and then left in place because the
dirty flag wasn't set?

Olivier Galibert writes:

 > Somebody please commit it, I changed ssh key recently (to go from ssh1
 > to ssh2) and haven't bothered Stephen with it yet.
 > 
 >   OG.
 > 
 > 2007-03-24   Olivier Galibert <galibert at pobox.com>
 > 
 > 	* chartab.c (Fcopy_char_table): Simplify the mirror table
 > 	handling: never copy a mirror table, just make a new one and mark
 > 	it dirty.  Fixes http://article.gmane.org/gmane.emacs.xemacs.beta/17353