Revert "Prevent overflow beyond the end of string in wtf_strwidth()"

This reverts commit d345c0950d.

libwc/wtf.c

@@ -120,14 +120,10 @@ int
 wtf_strwidth(wc_uchar *p)
 {
     int w = 0;
-    size_t len;
 
     while (*p) {
 	w += wtf_width(p);
-	len = WTF_LEN_MAP[*p];
-	if (len > strlen(p))
-	    len = strlen(p);
-	p += len;
+	p += WTF_LEN_MAP[*p];
     }
     return w;
 }