Dual license under MIT/APACHE the source code

This change is done for two reasons:
 - First, the Rust port is, as of the time of writing in an awkward
   position because he is dual license under MIT/APACHE instead of only
   the APACHE license. This change in license should fix this problem.
 - Second, and the most convincing reason is that there have been
   some discussion with the Rust Libs Team to integrate the Rust port
   directly into the Rust standard library.
   The license change is required because the code for every the Rust
   repository need's to dual license against MIT/APACHE.

Author: Urgau

LICENSE renamed to LICENSE-APACHE

@@ -0,0 +1,23 @@
+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.

LICENSE-MIT

@@ -150,3 +150,18 @@ invaluable feedback. Rémy Oudompheng first implemented a fast path we use in th
 
 The library includes code adapted from Google Wuffs (written by Nigel Tao) which was originally published 
 under the Apache 2.0 license.
+
+## License
+
+<sup>
+Licensed under either of <a href="LICENSE-APACHE">Apache License, Version
+2.0</a> or <a href="LICENSE-MIT">MIT license</a> at your option.
+</sup>
+
+<br>
+
+<sub>
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in this repository by you, as defined in the Apache-2.0 license,
+shall be dual licensed as above, without any additional terms or conditions.
+</sub>