Add public domain LICENSE and clarification in the README.txt

For issue #33

Author: eliben

LICENSE

@@ -0,0 +1,24 @@
+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/>

README.rst

@@ -76,3 +76,12 @@ with 'make', just run::
 Note that it expects to find binaries from the LLVM directory with which the
 samples were built and linked. Look at the ``emit_build_config`` rule in the
 Makefile for more information.
+
+License
+-------
+
+Unless stated otherwise, all the code in this repository is in the public
+domain. See the ``LICENSE`` file for more details. Some source files were taken
+almost verbatim from LLVM/Clang; for these, the LLVM license header comment is
+retained and LLVM's license applies (please see ``LICENSE.txt`` in the LLVM
+source tree).