Upgrade extract-idl.py for Python3; regenerate IDLs. (#3606)

Update to html5lib-1.1, and incorporate webencodings-0.5.1 dependency,
both of which which are required in order to run the extract-idl.py
script on python3. html5lib is MIT licensed and webencodings is BSD
licensed; both are compatible with this repository.

Regenerate WebGL 1.0 and 2.0 IDL from current specs.

resources/html5lib-1.1/LICENSE

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+Copyright (c) 2006-2013 James Graham and other contributors
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+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.

resources/html5lib-1.1/README.rst

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+html5lib
+========
+
+.. image:: https://travis-ci.org/html5lib/html5lib-python.svg?branch=master
+    :target: https://travis-ci.org/html5lib/html5lib-python
+
+
+html5lib is a pure-python library for parsing HTML. It is designed to
+conform to the WHATWG HTML specification, as is implemented by all major
+web browsers.
+
+
+Usage
+-----
+
+Simple usage follows this pattern:
+
+.. code-block:: python
+
+  import html5lib
+  with open("mydocument.html", "rb") as f:
+      document = html5lib.parse(f)
+
+or:
+
+.. code-block:: python
+
+  import html5lib
+  document = html5lib.parse("<p>Hello World!")
+
+By default, the ``document`` will be an ``xml.etree`` element instance.
+Whenever possible, html5lib chooses the accelerated ``ElementTree``
+implementation (i.e. ``xml.etree.cElementTree`` on Python 2.x).
+
+Two other tree types are supported: ``xml.dom.minidom`` and
+``lxml.etree``. To use an alternative format, specify the name of
+a treebuilder:
+
+.. code-block:: python
+
+  import html5lib
+  with open("mydocument.html", "rb") as f:
+      lxml_etree_document = html5lib.parse(f, treebuilder="lxml")
+
+When using with ``urllib2`` (Python 2), the charset from HTTP should be
+pass into html5lib as follows:
+
+.. code-block:: python
+
+  from contextlib import closing
+  from urllib2 import urlopen
+  import html5lib
+
+  with closing(urlopen("http://example.com/")) as f:
+      document = html5lib.parse(f, transport_encoding=f.info().getparam("charset"))
+
+When using with ``urllib.request`` (Python 3), the charset from HTTP
+should be pass into html5lib as follows:
+
+.. code-block:: python
+
+  from urllib.request import urlopen
+  import html5lib
+
+  with urlopen("http://example.com/") as f:
+      document = html5lib.parse(f, transport_encoding=f.info().get_content_charset())
+
+To have more control over the parser, create a parser object explicitly.
+For instance, to make the parser raise exceptions on parse errors, use:
+
+.. code-block:: python
+
+  import html5lib
+  with open("mydocument.html", "rb") as f:
+      parser = html5lib.HTMLParser(strict=True)
+      document = parser.parse(f)
+
+When you're instantiating parser objects explicitly, pass a treebuilder
+class as the ``tree`` keyword argument to use an alternative document
+format:
+
+.. code-block:: python
+
+  import html5lib
+  parser = html5lib.HTMLParser(tree=html5lib.getTreeBuilder("dom"))
+  minidom_document = parser.parse("<p>Hello World!")
+
+More documentation is available at https://html5lib.readthedocs.io/.
+
+
+Installation
+------------
+
+html5lib works on CPython 2.7+, CPython 3.5+ and PyPy. To install:
+
+.. code-block:: bash
+
+    $ pip install html5lib
+
+The goal is to support a (non-strict) superset of the versions that `pip
+supports
+<https://pip.pypa.io/en/stable/installing/#python-and-os-compatibility>`_.
+
+Optional Dependencies
+---------------------
+
+The following third-party libraries may be used for additional
+functionality:
+
+- ``lxml`` is supported as a tree format (for both building and
+  walking) under CPython (but *not* PyPy where it is known to cause
+  segfaults);
+
+- ``genshi`` has a treewalker (but not builder); and
+
+- ``chardet`` can be used as a fallback when character encoding cannot
+  be determined.
+
+
+Bugs
+----
+
+Please report any bugs on the `issue tracker
+<https://github.com/html5lib/html5lib-python/issues>`_.
+
+
+Tests
+-----
+
+Unit tests require the ``pytest`` and ``mock`` libraries and can be
+run using the ``py.test`` command in the root directory.
+
+Test data are contained in a separate `html5lib-tests
+<https://github.com/html5lib/html5lib-tests>`_ repository and included
+as a submodule, thus for git checkouts they must be initialized::
+
+  $ git submodule init
+  $ git submodule update
+
+If you have all compatible Python implementations available on your
+system, you can run tests on all of them using the ``tox`` utility,
+which can be found on PyPI.
+
+
+Questions?
+----------
+
+There's a mailing list available for support on Google Groups,
+`html5lib-discuss <http://groups.google.com/group/html5lib-discuss>`_,
+though you may get a quicker response asking on IRC in `#whatwg on
+irc.freenode.net <http://wiki.whatwg.org/wiki/IRC>`_.