[Unlicense] Convert to SPDX license format

LICENSES/Unlicense

@@ -0,0 +1,30 @@
+Valid-License-Identifier: Unlicense
+SPDX-URL: https://spdx.org/licenses/Unlicense.html
+Usage-Guide:
+  To use the Unlicense put the following SPDX tag/value pair into a
+  comment according to the placement guidelines in the licensing rules
+  documentation:
+    SPDX-License-Identifier: Unlicense
+License-Text:
+
+This is free and unencumbered software released into the public domain.
+
+Anyone is free to copy, modify, publish, use, compile, sell, or distribute
+this software, either in source code form or as a compiled binary, for any
+purpose, commercial or non-commercial, and by any means.
+
+In jurisdictions that recognize copyright laws, the author or authors of this
+software dedicate any and all copyright interest in the software to the public
+domain. We make this dedication for the benefit of the public at large and
+to the detriment of our heirs and successors. We intend this dedication to be
+an overt act of relinquishment in perpetuity of all present and future rights
+to this software under copyright law.
+
+THE SOFTWARE IS 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. IN NO EVENT SHALL THE AUTHORS
+BE 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.
+
+For more information, please refer to <http://unlicense.org/>

test/doit.c

@@ -1,6 +1,11 @@
-/* this program is in the public domain 
-   A program that helps the authors of the fine fftw library benchmark kiss 
-*/
+/*
+ *  This program is in the public domain 
+ *  A program that helps the authors of the fine fftw library benchmark kiss 
+ *  This file is part of KISS FFT - https://github.com/mborgerding/kissfft
+ *
+ *  SPDX-License-Identifier: Unlicense
+ *  See LICENSES/Unlicense for more information.
+ */
 
 #include "bench-user.h"
 #include <math.h>