(merge from 3.2) Issue #9516: avoid errors in sysconfig when MACOSX_DEPLOYMENT_TARGET...

Without this patch python will fail to start properly when the environment
variable MACOSX_DEPLOYMENT_TARGET is set on MacOSX and has a value that is
not compatible with the value during Python's build. This is caused by code
in sysconfig that was only meant to be used in disutils.

diff --cc Misc/NEWS
index 04c4fbcf98309914c72d1f39f116c99a95ff7a70,00a370452976d4ec780bb2fbc356f5b7c1d92f8d..3e8f474dcbf19f2173357a198a68075083f7c172
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -153,63 -158,8 +153,66 @@@ Core and Builtin
  Library
  -------
  
 -- Issue #11927: SMTP_SSL now uses port 465 by default as documented.  Patch by
 -  Kasun Herath.
++- Issue #9516: Issue #9516: avoid errors in sysconfig when MACOSX_DEPLOYMENT_TARGET
++  is set in shell.
++
 +- Issue #8650: Make zlib module 64-bit clean. compress(), decompress() and
 +  their incremental counterparts now raise OverflowError if given an input
 +  larger than 4GB, instead of silently truncating the input and returning
 +  an incorrect result.
 +
 +- Issue #12050: zlib.decompressobj().decompress() now clears the unconsumed_tail
 +  attribute when called without a max_length argument.
 +
 +- Issue #12062: Fix a flushing bug when doing a certain type of I/O sequence
 +  on a file opened in read+write mode (namely: reading, seeking a bit forward,
 +  writing, then seeking before the previous write but still within buffered
 +  data, and writing again).
 +
 +- Issue #9971: Write an optimized implementation of BufferedReader.readinto().
 +  Patch by John O'Connor.
 +
 +- Issue #1028: Tk returns invalid Unicode null in %A: UnicodeDecodeError.
 +  With Tk < 8.5 _tkinter.c:PythonCmd() raised UnicodeDecodeError, caused
 +  IDLE to exit.  Converted to valid Unicode null in PythonCmd().
 +
 +- Issue #11799: urllib.request Authentication Handlers will raise a ValueError
 +  when presented with an unsupported Authentication Scheme. Patch contributed
 +  by Yuval Greenfield.
 +
 +- Issue #10419, #6011: build_scripts command of distutils handles correctly
 +  non-ASCII path (path to the Python executable). Open and write the script in
 +  binary mode, but ensure that the shebang is decodable from UTF-8 and from the
 +  encoding of the script.
 +
 +- Issue #8498: In socket.accept(), allow to specify 0 as a backlog value in
 +  order to accept exactly one connection.  Patch by Daniel Evers.
 +
 +- Issue #12011: signal.signal() and signal.siginterrupt() raise an OSError,
 +  instead of a RuntimeError: OSError has an errno attribute.
 +
 +- Issue #3709: a flush_headers method to BaseHTTPRequestHandler which manages
 +  the sending of headers to output stream and flushing the internal headers
 +  buffer. Patch contribution by Andrew Schaaf
 +
 +- Issue #11743: Rewrite multiprocessing connection classes in pure Python.
 +
 +- Issue #11164: Stop trying to use _xmlplus in the xml module.
 +
 +- Issue #11888: Add log2 function to math module. Patch written by Mark
 +  Dickinson.
 +
 +- Issue #12012: ssl.PROTOCOL_SSLv2 becomes optional.
 +
 +- Issue #8407: The signal handler writes the signal number as a single byte
 +  instead of a nul byte into the wakeup file descriptor. So it is possible to
 +  wait more than one signal and know which signals were raised.
 +
 +- Issue #8407: Add pthread_kill(), sigpending() and sigwait() functions to the
 +  signal module.
 +
 +- Issue #11927: SMTP_SSL now uses port 465 by default as documented.  Patch
 +  by Kasun Herath.
  
  - Issue #12002: ftplib's abort() method raises TypeError.