the C code, using pipe2() when available.  Adds unittests for close_fds and
cloexec behaviors.

platform basis.  It remains False on Windows and changes to True on all
other platforms (POSIX).  Based on python-dev discussion and
http://bugs.python.org/issue7213.

When the solution is converted to Visual Studio 2010, the command line to invoke make_buildinfo changes from:
$(SolutionDir)make_buildinfo.exe" Debug "$(IntDir)\"
to
$(SolutionDir)make_buildinfo.exe" Debug "$(IntDir)"
If the final backslash is omitted, the backslash in IntDir will escape the quote, thus passing the quote in as part of the path name.

This solution is a hack-fix to that problem by skipping any trailing quote from the path name.  It works as long as we don't need any additional arguments to make_buildinfo.exe.  This will help all those sould that are going to run this project through the visual studio autoconverter and get the same error.

The rearranged code should do exactly what the old code did, but
the new code avoids a potentially costly re computation in the case
where a boundary already exists.

Issue #10188 (partial resolution): tidy up some behaviour in the new tempfile.TemporaryDirectory context manager

instead of bininstall target so it shows up when you do 'make altinstall'.
Closes issue 10677.