Refine LICENSE and README about code parts covered by MIT and GPL-2.0

* LICENSE: Mention MIT and GPL-2.0 at the top of the file; copy
copyrights from README.md; group all copyrights in one block;
explicitly specify which code is covered by MIT and which one by GPL;
remove a statement about the possibility of license change in future.
* README.md: Refine the statement about new code to use C11 atomics;
specify license type at the top of the file.
* README.md (Overview): Mention that README_malloc.txt and
README_stack.txt describe the functionality of libatomic_ops_gpl.
* README.md (Installation and Usage): Mention that libatomic_ops.a is
a core library and libatomic_ops_gpl.a is a gpl extension library;
mention that libatomic_ops_gpl.a licensing details are given in
COPYING and LICENSE files.
* README.md (Copyright & Warranty): Rename to
"Copyright & Warranty, Contributors"; remove all copyrights (they are
moved to LICENSE); better explain the dual nature of the license.

1 files changed, 22 insertions, 31 deletions

diff --git a/README.md b/README.md
index 9c77f96..a4fde5c 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,7 @@
 # The atomic_ops library (`libatomic_ops`)
 
-IN NEW CODE, PLEASE USE C11 OR C++14 STANDARD ATOMICS INSTEAD OF THIS PACKAGE.
+IN NEW CODE, PLEASE USE C11 OR C++14 STANDARD ATOMICS INSTEAD OF THE CORE
+LIBRARY IN THIS PACKAGE.
 
 [![Travis-CI build status](https://travis-ci.com/ivmai/libatomic_ops.svg?branch=master)](https://travis-ci.com/ivmai/libatomic_ops)
 [![AppVeyor CI build status](https://ci.appveyor.com/api/projects/status/github/ivmai/libatomic_ops?branch=master&svg=true)](https://ci.appveyor.com/project/ivmai/libatomic-ops)
@@ -18,6 +19,9 @@ IN NEW CODE, PLEASE USE C11 OR C++14 STANDARD ATOMICS INSTEAD OF THIS PACKAGE.
 
 This is version 7.7.0 (next release development) of libatomic_ops.
 
+License: [MIT](LICENSE) for core library / [GPL-2.0](COPYING) for gpl
+extension.
+
 
 ## Download
 
@@ -50,10 +54,10 @@ Please see other README files for the details:
 * [README_details.txt](README_details.txt) - details about atomic_ops.h
 
 * [README_malloc.txt](README_malloc.txt) - a simple almost-lock-free malloc
-  implementation
+  implementation (part of libatomic_ops_gpl)
 
 * [README_stack.txt](README_stack.txt) -  an almost lock-free LIFO linked
-  lists (stack) implementation
+  lists (stack) implementation (part of libatomic_ops_gpl)
 
 
 ## Installation and Usage
@@ -70,17 +74,18 @@ Alternatively, CMake could be use to build this package, e.g.
 Note that much of the content of this library is in the header files.
 However, two small libraries are built and installed:
 
-* `libatomic_ops.a` is a support library, which is not needed on some
+* `libatomic_ops.a` is a support (core) library, which is not needed on some
   platforms. This is intended to be usable, under some mild restrictions,
   in free or proprietary code, as are all the header files.
   See [LICENSE](LICENSE) for more details about the licensing.
 
-* `libatomic_ops_gpl.a` contains some higher level facilities.  This code is
-  currently covered by the GPL.  The contents currently correspond to
-  the headers `atomic_ops_malloc.h` and `atomic_ops_stack.h`.  Not built and
-  not installed if `--disable-gpl` option is passed to `configure` (or if
-  `-Denable_gpl=OFF` option is passed to `cmake` if the latter is used to
-  build the package).
+* `libatomic_ops_gpl.a` is a so called gpl extension library containing some
+  higher level facilities.  This code is covered by the GPL.  The contents
+  correspond to the headers `atomic_ops_malloc.h` and `atomic_ops_stack.h`.
+  Not built and not installed if `--disable-gpl` option is passed to
+  `configure` (or if `-Denable_gpl=OFF` option is passed to `cmake` if the
+  latter is used to build the package).  The licensing details are given in
+  [COPYING](COPYING) and [LICENSE](LICENSE) files.
 
 
 ## Platform Specific Notes
@@ -124,30 +129,16 @@ To be notified on all issues, please
 GitHub.
 
 
-## Copyright & Warranty
-
- * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
- * Copyright (c) 1996-1999 by Silicon Graphics.  All rights reserved.
- * Copyright (c) 1999-2011 Hewlett-Packard Development Company, L.P.
- * Copyright (c) 2008-2021 Ivan Maidanski
-
-The file armcc/arm_v6.h is also
-
- * Copyright (c) 2007 by NEC LE-IT.  All rights reserved.
-
-The file gcc/avr32.h is
-
- * Copyright (c) 2009 Bradley Smith <brad@brad-smith.co.uk>
-
-The file gcc/mips.h is
+## Copyright & Warranty, Contributors
 
- * Copyright (c) 2005, 2007 Thiemo Seufer <ths@networkno.de>
+Please be aware of the dual nature of the license of libatomic_ops:
 
-The file gcc/sh.h is
+* the core part (implementing semi-portable access to hardware-provided
+  atomic memory operations) is released under MIT license
 
- * Copyright (c) 2009 by Takashi YOSHII. All rights reserved.
+* the gpl extension (almost lock-free malloc and stack implementations) and
+  the tests are released under GPL-2.0 license
 
-Please be aware of the dual nature of the license of libatomic_ops, see
-[LICENSE](LICENSE) for the details.
+The exact licensing information is provided in [LICENSE](LICENSE) file.
 
 The library contributors are listed in [AUTHORS](AUTHORS) file.