This changes the main documentation, doc strings, source code comments, and a
couple error messages in the test suite. In some cases the word was removed
or edited some other way to fix the grammar.

In Python 3.3, PyThread_set_key_value() did nothing if the key already exists
(if the current value is a non-NULL pointer).

When _PyGILState_NoteThreadState() is called twice on the same thread with a
different Python thread state, it still keeps the old Python thread state to
keep the old behaviour. Replacing the Python thread state with the new state
introduces new bugs: see issues #10915 and #15751.

test_capi is failing and the fix is not trivial, I prefer to revert

the function did nothing if the key already exists (if the current value is a
non-NULL pointer).

_testcapi.run_in_subinterp() now correctly sets the new Python thread state of
the current thread when a subinterpreter is created.

PyStructSequence_InitType() except that it has a return value (0 on success,
-1 on error).

 * PyStructSequence_InitType2() now raises MemoryError on memory allocation failure
 * Fix also some calls to PyDict_SetItemString(): handle error

* Replace malloc() with PyMem_RawMalloc()
* Replace PyMem_Malloc() with PyMem_RawMalloc() where the GIL is not held.
* _Py_char2wchar() now returns a buffer allocated by PyMem_RawMalloc(), instead
  of PyMem_Malloc()

(following PEP 11).  These systems are systems using Mach C Threads,
SunOS lightweight processes, GNU pth threads and IRIX threads.