libedit: Disable -Wuse-after-free for chartype.c.

GCC 12 thinks ct_visual_string can reuse a pointer after it has been
reallocated, but in this case the warning appears false.

Reviewed by:	emaste
Differential Revision:	https://reviews.freebsd.org/D36820

lib/libedit/Makefile

@@ -97,3 +97,5 @@ test: tc1.o libedit.a ${DPADD} ${LIBTERMCAP}
 	${CC} ${CFLAGS} ${.ALLSRC} -o ${.TARGET} libedit.a ${LDADD}
 
 .include <bsd.lib.mk>
+
+CWARNFLAGS.chartype.c=	${NO_WUSE_AFTER_FREE}