Expand kadmin protocol kvno range

Make xdr_krb5_kvno() use xdr_u_int() instead of xdr_u_char(), allowing
it to marshal kvno values up to 32 bits.  This change is
backwards-compatible because XDR uses four bytes to marshal char
values and does no bounds checking of char values on decode.

ticket: 7532

src/lib/kadm5/kadm_rpc_xdr.c

@@ -136,20 +136,7 @@ xdr_krb5_timestamp(XDR *xdrs, krb5_timestamp *objp)
 bool_t
 xdr_krb5_kvno(XDR *xdrs, krb5_kvno *objp)
 {
-	unsigned char tmp;
-
-	tmp = '\0'; /* for purify, else xdr_u_char performs a umr */
-
-	if (xdrs->x_op == XDR_ENCODE)
-		tmp = (unsigned char) *objp;
-
-	if (!xdr_u_char(xdrs, &tmp))
-		return (FALSE);
-
-	if (xdrs->x_op == XDR_DECODE)
-		*objp = (krb5_kvno) tmp;
-
-	return (TRUE);
+	return xdr_u_int(xdrs, objp);
 }
 
 bool_t