Issue #112: Prepare Stackless 3.5, fix a C-Python test suite bug

This commit merges the fix from C-Python pull request
python#1066 (git commit 22e032a) for
bpo-30028. Without this change
   $ ./python -m test.regrtest test_multiprocessing_fork
fails. ($ ./python -m test.test_multiprocessing_fork is OK.)

https://bitbucket.org/stackless-dev/stackless/issues/112
(grafted from bda8a9d487da7cfbe4357d5c4c7635e0de19c6af)

Lib/test/support/__init__.py

@@ -902,10 +902,12 @@ def temp_dir(path=None, quiet=False):
                 raise
             warnings.warn('tests may fail, unable to create temp dir: ' + path,
                           RuntimeWarning, stacklevel=3)
+    if dir_created:
+        pid = os.getpid()
     try:
         yield path
     finally:
-        if dir_created:
+        if dir_created and pid == os.getpid():
             shutil.rmtree(path)
 
 @contextlib.contextmanager