Read from NULL raises SIGILL, not SIGSEGV, on Mac OS X Lion.

Confirm that the prime example is actually correct.  We get so many complaints about a "buggy example" on docs@python, let us hope this cuts them in half at least.

- Move a test from call time to define time
- Add the function name to __all__
- Improve docstring and docs

A few lines are now duplicated (named tuple definition and docstring)
but I think the end result reads better.

In the install and library docs, I changed the text to refer to
packaging instead of distutils.  I also checked that the documented
paths correctly reflect what’s really defined in sysconfig; the main
difference with paths defined in distutils.install is that include
directories don’t end with the distribution name anymore (i.e. distutils
uses include/python3.3/spam, sysconfig include/python3.3), I have no
idea why.

This started out as an easy task, just add a section describing this
alternate scheme, but I found a lot of cleanup to do along the way:

- fixed inverted reST targets
- fixed entries for modules (hi abiflags!) or data files
- avoided duplicating the same options listing five or six times
- added missing entries for C headers locations
- added documentation for --install-lib
- fixed a few misuses of the option role (see #9312), but not all (not
  worth the time, but will do it in packaging docs)
- fixed some markup

The paths fixes were done with an eye on the source code in the install
command, so they really describe what’s actually done.  The situation on
Mac OS X is rather messy: the fix for #8084 touched site and sysconfig,
but distutils doesn’t use these files.  I suspect we have a mismatched
stdlib at the moment, and the fix is not even clear (see the bug report
for further discussion).

merge from 3.2 - Fix closes issue12698 - make the no_proxy environment variable handling a bit lenient (accomodate spaces in between the items)