Final cleanup of license status for Juliet tasks

Fixes #1018

We also label the readme's with the same license as the sources
because they were submitted together by the respective contributors
and thus can be assumed to be under the same license.

The original C sources for Juliet tasks get a general license statement
in .reuse/dep5 because it is probably not worth it to change all of
these files.
For example, users of this repo who wish to redistribute parts of it
(e.g., in artifacts) will likely redistribute only the actual task
files, so for the task files the REUSE compatibility provides a benefit.

Author: PhilippWendler

.reuse/dep5

@@ -10,6 +10,11 @@ Files:
 Copyright: 2011-2020 The SV-Benchmarks Community
 License: CC0-1.0
 
+Files: c/Juliet_Test/Juliet_Test_Suite_v1.3_for_C_Cpp
+ _
+Copyright: 2010-2020 NIST
+License: CC0-1.0
+
 Files:
  clauses
  c/bitvector
@@ -31,7 +36,6 @@ Copyright: unknown
 License: LicenseRef-unknown
 
 Files:
- c/Juliet_Test
  c/array-cav19
  c/array-crafted
  c/array-examples
@@ -153,7 +157,6 @@ Files:
  java/jdart-regression
  java/jdart-regression
  java/jpf-regression
- java/juliet-java
  _
 Copyright: unknown
 License: LicenseRef-in-text-file

c/Juliet_Test/LICENSE.txt

@@ -1,3 +1,12 @@
+<!--
+This file is part of the SV-Benchmarks collection of verification tasks:
+https://github.com/sosy-lab/sv-benchmarks
+
+SPDX-FileCopyrightText: 2020 The SV-Benchmarks Community
+
+SPDX-License-Identifier: CC0-1.0
+-->
+
 These benchmarks were generated from Juliet Test Suite for C/C++ version 1.3 by Anton Vasilyev, Linux Verification Center, ISPRAS. 
 
 Juliet Test Suite home page: https://samate.nist.gov/SRD/testsuite.php
@@ -6,6 +15,4 @@ Description: A collection of test cases in the C/C++ language. It contains examp
 
 All documents related to the Juliet Test Suite can be found at the documents page.
 
-This software is not subject to copyright protection and is in the public domain. NIST assumes no responsibility whatsoever for its use by other parties, and makes no guaranties, expressed or implied, about its quality, reliability, or any other characteristic.
-
 Contributor: NSA Center for Assured Software

c/Juliet_Test/README.txt renamed to c/Juliet_Test/README.md

@@ -1,3 +1,12 @@
+<!--
+This file is part of the SV-Benchmarks collection of verification tasks:
+https://github.com/sosy-lab/sv-benchmarks
+
+SPDX-FileCopyrightText: 2020 The SV-Benchmarks Community
+
+SPDX-License-Identifier: CC0-1.0
+-->
+
 All benchmarks in this folder are derivations from the Juliet V1.3 Java Benchmark
 created by the NIST and published at: https://samate.nist.gov/SARD/testsuite.php