build(tools): list lz4-java, LZ4 and xxHash in the shaded jar LICENSE

arrow-tools shades lz4-java, including the native libraries it ships.
lz4-java 1.12.1 pins LZ4 at v1.10.0 and builds those libraries from
lz4.c, lz4hc.c and xxhash.c in LZ4's lib directory, so they contain
LZ4 1.10.0 and the xxHash 0.6.5 copy there, both under the BSD
2-Clause license. Add entries for all three, with the BSD texts inline.
lz4-java has no NOTICE file, so NOTICE.txt is unchanged.

Author: andygrove

tools/src/shade/LICENSE.txt

@@ -329,3 +329,82 @@ License text:
 | 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 binary artifact contains lz4-java 1.12.1.
+
+Copyright: Copyright 2020 Adrien Grand and the lz4-java contributors.
+Home page: https://github.com/yawkat/lz4-java
+License: https://www.apache.org/licenses/LICENSE-2.0
+
+--------------------------------------------------------------------------------
+
+This binary artifact contains LZ4 1.10.0, in the native libraries of lz4-java.
+
+Copyright: Copyright (c) 2011-2020, Yann Collet
+Home page: https://github.com/lz4/lz4
+License: BSD 2-Clause License
+License text:
+
+| LZ4 Library
+| Copyright (c) 2011-2020, Yann Collet
+| All rights reserved.
+|
+| Redistribution and use in source and binary forms, with or without modification,
+| are permitted provided that the following conditions are met:
+|
+| * Redistributions of source code must retain the above copyright notice, this
+|   list of conditions and the following disclaimer.
+|
+| * Redistributions in binary form must reproduce the above copyright notice, this
+|   list of conditions and the following disclaimer in the documentation and/or
+|   other materials provided with the distribution.
+|
+| THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+| ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+| WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+| DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+| ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+| (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+| LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+| ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+| (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+| SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+--------------------------------------------------------------------------------
+
+This binary artifact contains xxHash 0.6.5, in the native libraries of lz4-java.
+
+Copyright: Copyright (C) 2012-2016, Yann Collet
+Home page: https://github.com/Cyan4973/xxHash
+License: BSD 2-Clause License
+License text:
+
+| xxHash - Extremely Fast Hash algorithm
+| Copyright (C) 2012-2016, Yann Collet.
+|
+| BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
+|
+| Redistribution and use in source and binary forms, with or without
+| modification, are permitted provided that the following conditions are
+| met:
+|
+|     * Redistributions of source code must retain the above copyright
+| notice, this list of conditions and the following disclaimer.
+|     * Redistributions in binary form must reproduce the above
+| copyright notice, this list of conditions and the following disclaimer
+| in the documentation and/or other materials provided with the
+| distribution.
+|
+| THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+| "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+| LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+| A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+| OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+| SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+| LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+| DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+| THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+| (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+| OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.