Auto merge of #1846 - RalfJung:license, r=RalfJung

sync license files with rustc repo

`@Mark-Simulacrum` pointed out that our license files are slightly different from those in rustc. This syncs them.

The question is... is this a thing we can just do?^^

Author: bors

LICENSE-APACHE

@@ -174,28 +174,3 @@ TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
    of your accepting any such warranty or additional liability.
 
 END OF TERMS AND CONDITIONS
-
-APPENDIX: How to apply the Apache License to your work.
-
-   To apply the Apache License to your work, attach the following
-   boilerplate notice, with the fields enclosed by brackets "[]"
-   replaced with your own identifying information. (Don't include
-   the brackets!)  The text should be enclosed in the appropriate
-   comment syntax for the file format. We also recommend that a
-   file or class name and description of purpose be included on the
-   same "printed page" as the copyright notice for easier
-   identification within third-party archives.
-
-Copyright 2016 The Miri Developers
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.

LICENSE-MIT

@@ -1,5 +1,3 @@
-Copyright (c) 2016 The Miri 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