Add bundled licenses documentation

Also includes in the bundled tarball artifact.

docs/bundled_licenses/python-crypto.txt

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+Copyright and licensing of the Python Cryptography Toolkit ("PyCrypto"):
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Previously, the copyright and/or licensing status of the Python
+Cryptography Toolkit ("PyCrypto") had been somewhat ambiguous.  The
+original intention of Andrew M. Kuchling and other contributors has
+been to dedicate PyCrypto to the public domain, but that intention was
+not necessarily made clear in the original disclaimer (see
+LEGAL/copy/LICENSE.orig).
+
+Additionally, some files within PyCrypto had specified their own
+licenses that differed from the PyCrypto license itself.  For example,
+the original RIPEMD.c module simply had a copyright statement and
+warranty disclaimer, without clearly specifying any license terms.
+(An updated version on the author's website came with a license that
+contained a GPL-incompatible advertising clause.)
+
+To rectify this situation for PyCrypto 2.1, the following steps have
+been taken:
+
+ 1. Obtaining explicit permission from the original contributors to
+    dedicate their contributions to the public domain if they have not
+    already done so.  (See the "LEGAL/copy/stmts" directory for
+    contributors' statements.)
+
+ 2. Replacing some modules with clearly-licensed code from other
+    sources (e.g. the DES and DES3 modules were replaced with new ones
+    based on Tom St. Denis's public-domain LibTomCrypt library.)
+
+ 3. Replacing some modules with code written from scratch (e.g. the
+    RIPEMD and Blowfish modules were re-implemented from their
+    respective algorithm specifications without reference to the old
+    implementations).
+
+ 4. Removing some modules altogether without replacing them.
+
+To the best of our knowledge, with the exceptions noted below or
+within the files themselves, the files that constitute PyCrypto are in
+the public domain.  Most are distributed with the following notice:
+
+  The contents of this file are dedicated to the public domain.  To
+  the extent that dedication to the public domain is not available,
+  everyone is granted a worldwide, perpetual, royalty-free,
+  non-exclusive license to exercise all rights associated with the
+  contents of this file for any purpose whatsoever.
+  No rights are reserved.
+
+  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 OR COPYRIGHT HOLDERS
+  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.
+
+Exception:
+
+ - Portions of HMAC.py and setup.py are derived from Python 2.2, and
+   are therefore Copyright (c) 2001, 2002, 2003 Python Software
+   Foundation (All Rights Reserved).  They are licensed by the PSF
+   under the terms of the Python 2.2 license.  (See the file
+   LEGAL/copy/LICENSE.python-2.2 for details.)
+
+EXPORT RESTRICTIONS:
+
+Note that the export or re-export of cryptographic software and/or
+source code may be subject to regulation in your jurisdiction.
+