Adding cython v0.20.2 in third-party.

third_party/cython/src/README.txt

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+Welcome to Cython!
+=================
+
+Cython (http://cython.org) is a language that makes writing C extensions for
+the Python language as easy as Python itself.  Cython is based on the
+well-known Pyrex, but supports more cutting edge functionality and
+optimizations.
+
+The Cython language is very close to the Python language, but Cython
+additionally supports calling C functions and declaring C types on variables
+and class attributes.  This allows the compiler to generate very efficient C
+code from Cython code.
+
+This makes Cython the ideal language for wrapping external C libraries, and
+for fast C modules that speed up the execution of Python code.
+
+LICENSE:
+
+The original Pyrex program was licensed "free of restrictions" (see
+below).  Cython itself is licensed under the permissive
+
+   Apache License
+
+See LICENSE.txt.
+
+
+--------------------------
+
+Note that Cython used to ship the full version control repository in its source
+distribution, but no longer does so due to space constraints.  To get the
+full source history, make sure you have git installed, then step into the
+base directory of the Cython source distribution and type
+
+    make repo
+
+Alternatively, check out the latest developer repository from
+
+    https://github.com/cython/cython
+
+
+
+The following is from Pyrex:
+------------------------------------------------------
+This is a development version of Pyrex, a language
+for writing Python extension modules.
+
+For more info, see:
+
+    Doc/About.html for a description of the language
+    INSTALL.txt    for installation instructions
+    USAGE.txt      for usage instructions
+    Demos          for usage examples
+
+Comments, suggestions, bug reports, etc. are
+welcome!
+
+Copyright stuff: Pyrex is free of restrictions. You
+may use, redistribute, modify and distribute modified
+versions.
+
+The latest version of Pyrex can be found here:
+
+http://www.cosc.canterbury.ac.nz/~greg/python/Pyrex/
+
+Greg Ewing, Computer Science Dept, +--------------------------------------+
+University of Canterbury,          | A citizen of NewZealandCorp, a       |
+Christchurch, New Zealand          | wholly-owned subsidiary of USA Inc.  |
+greg@cosc.canterbury.ac.nz         +--------------------------------------+