[docs] Update cgi module doc (issue 11352)

[jimjjewett at gmail.com]

http://bugs.python.org/review/11352/diff/4862/Doc/library/cgi.rst
File Doc/library/cgi.rst (right):

http://bugs.python.org/review/11352/diff/4862/Doc/library/cgi.rst#newcode32
Doc/library/cgi.rst:32: submitted through an HTML ``<FORM>`` element.
Marking for posterity:  ISINDEX is obsolete, but still supported.  This
change is OK anyhow because of the "usually".

http://bugs.python.org/review/11352/diff/4862/Doc/library/cgi.rst#newcode95
Doc/library/cgi.rst:95: consume standard input, it should be
instantiated only once.
Once once per what?  Per Request?  Per process?  Per process until the
previous instantiation has finished its work, and can be finalized?

http://bugs.python.org/review/11352/diff/4862/Doc/library/cgi.rst#newcode99
Doc/library/cgi.rst:99: is usually contained in the META tag in the HEAD
section of the HTML
Also, "in a META element", rather than *the* element.

Also, encoding depends on the data uploaded, not just on the form sent. 
I'm not sure how to word that, but here is a try:

The *encoding* and *errors* parameters indicate how to decode the bytes
into text strings.  (See the :mod:`str` documentation.)  The default
assumption is ASCII, with any other characters causing an exception to
be raised.  Often, a better guess is available, typically from
application- (or form-) specific knowledge, a :mailheader:`Content-Type`
header's `charset` attribute, or a  ``<META>`` element.


Note that I agree a link might be better still; I'm just not sure how to
do it.

http://bugs.python.org/review/11352/diff/4862/Doc/make.bat
File Doc/make.bat (right):

http://bugs.python.org/review/11352/diff/4862/Doc/make.bat#newcode5
Doc/make.bat:5: if "%PYTHON%" EQU "" set PYTHON=c:/python27/python.exe
This seems like a change to for bootstrapping or cross-compiling --
unrelated to the doc changes.

http://bugs.python.org/review/11352/diff/4862/Lib/http/server.py
File Lib/http/server.py (right):

http://bugs.python.org/review/11352/diff/4862/Lib/http/server.py#newcode1167
Lib/http/server.py:1167: stdin=stdin,
This change is not just documentation, and should probably be discussed
separately.

http://bugs.python.org/review/11352/