syntax/license: add the unicode license for unicode-tables

Add the Unicode license to the unicode-tables directory, as the data
there comes from the Unicode Consortium.

Fixes #530

Author: Derek Gonyeo

README.md

@@ -232,3 +232,7 @@ This project is licensed under either of
    http://opensource.org/licenses/MIT)
 
 at your option.
+
+The data in `regex-syntax/src/unicode_tables/` is licensed under the Unicode
+License Agreement
+([LICENSE-UNICODE](http://www.unicode.org/copyright.html#License).

regex-syntax/src/unicode_tables/LICENSE-UNICODE

@@ -0,0 +1,57 @@
+UNICODE, INC. LICENSE AGREEMENT - DATA FILES AND SOFTWARE
+
+Unicode Data Files include all data files under the directories
+http://www.unicode.org/Public/, http://www.unicode.org/reports/,
+http://www.unicode.org/cldr/data/, http://source.icu-project.org/repos/icu/, and
+http://www.unicode.org/utility/trac/browser/.
+
+Unicode Data Files do not include PDF online code charts under the
+directory http://www.unicode.org/Public/.
+
+Software includes any source code published in the Unicode Standard
+or under the directories
+http://www.unicode.org/Public/, http://www.unicode.org/reports/,
+http://www.unicode.org/cldr/data/, http://source.icu-project.org/repos/icu/, and
+http://www.unicode.org/utility/trac/browser/.
+
+NOTICE TO USER: Carefully read the following legal agreement.
+BY DOWNLOADING, INSTALLING, COPYING OR OTHERWISE USING UNICODE INC.'S
+DATA FILES ("DATA FILES"), AND/OR SOFTWARE ("SOFTWARE"),
+YOU UNEQUIVOCALLY ACCEPT, AND AGREE TO BE BOUND BY, ALL OF THE
+TERMS AND CONDITIONS OF THIS AGREEMENT.
+IF YOU DO NOT AGREE, DO NOT DOWNLOAD, INSTALL, COPY, DISTRIBUTE OR USE
+THE DATA FILES OR SOFTWARE.
+
+COPYRIGHT AND PERMISSION NOTICE
+
+Copyright © 1991-2018 Unicode, Inc. All rights reserved.
+Distributed under the Terms of Use in http://www.unicode.org/copyright.html.
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Unicode data files and any associated documentation
+(the "Data Files") or Unicode software and any associated documentation
+(the "Software") to deal in the Data Files or Software
+without restriction, including without limitation the rights to use,
+copy, modify, merge, publish, distribute, and/or sell copies of
+the Data Files or Software, and to permit persons to whom the Data Files
+or Software are furnished to do so, provided that either
+(a) this copyright and permission notice appear with all copies
+of the Data Files or Software, or
+(b) this copyright and permission notice appear in associated
+Documentation.
+
+THE DATA FILES AND SOFTWARE ARE 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 OF THIRD PARTY RIGHTS.
+IN NO EVENT SHALL THE COPYRIGHT HOLDER OR HOLDERS INCLUDED IN THIS
+NOTICE BE LIABLE FOR ANY CLAIM, OR ANY SPECIAL INDIRECT OR CONSEQUENTIAL
+DAMAGES, OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+PERFORMANCE OF THE DATA FILES OR SOFTWARE.
+
+Except as contained in this notice, the name of a copyright holder
+shall not be used in advertising or otherwise to promote the sale,
+use or other dealings in these Data Files or Software without prior
+written authorization of the copyright holder.