Correct license header in zbase32 to match original work

The original work is licensed dual MIT+Apache-2 just like us, so
the license header should not only mention MIT.

Author: TheBlueMatt

lightning/src/util/zbase32.rs

@@ -1,26 +1,11 @@
 // This is a modification of base32 encoding to support the zbase32 alphabet.
 // The original piece of software can be found at https://github.com/andreasots/base32
+// The original portions of this software are Copyright (c) 2015 The base32 Developers
 
-/*
-Copyright (c) 2015 The base32 Developers
-
-Permission is hereby granted, free of charge, to any person obtaining a copy
-of this software and associated documentation files (the "Software"), to deal
-in the Software without restriction, including without limitation the rights
-to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-copies of the Software, and to permit persons to whom the Software is
-furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all
-copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.
+/* This file is licensed under either of
+ *  Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0) or
+ *  MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
+ * at your option.
 */
 
 const ALPHABET: &'static [u8] = b"ybndrfg8ejkmcpqxot1uwisza345h769";