Also, improve some docstring descriptions of the 'errors' parameter.

Closes #14015.

exec runs into an error.  Prevent a regular multi-close of the /dev/null
fd when any of stdin, stdout and stderr was set to DEVNULL.

exec runs into an error.  Prevent a regular multi-close of the /dev/null
fd when any of stdin, stdout and stderr was set to DEVNULL.

Reported by Atsuo Ishimoto.

source_from_cache(), finishing the work introduced in changset
4134:9cacdb9d0c59.

module and not as a definition of what an enumeration is.

The new API require more discussion.

Missing files added.
News entry added.

allowing for documenting imp.new_module() as deprecated.

deprecation of imp.get_magic().

* Add a new PyMemAllocators structure
* New functions:

  - PyMem_RawMalloc(), PyMem_RawRealloc(), PyMem_RawFree(): GIL-free memory
    allocator functions
  - PyMem_GetRawAllocators(), PyMem_SetRawAllocators()
  - PyMem_GetAllocators(), PyMem_SetAllocators()
  - PyMem_SetupDebugHooks()
  - _PyObject_GetArenaAllocators(), _PyObject_SetArenaAllocators()

* Add unit test for PyMem_Malloc(0) and PyObject_Malloc(0)
* Add unit test for new get/set allocators functions
* PyObject_Malloc() now falls back on PyMem_Malloc() instead of malloc() if
  size is bigger than SMALL_REQUEST_THRESHOLD, and PyObject_Realloc() falls
  back on PyMem_Realloc() instead of realloc()
* PyMem_Malloc() and PyMem_Realloc() now always call malloc() and realloc(),
  instead of calling PyObject_Malloc() and PyObject_Realloc() in debug mode