Issue #16248: Disable code execution from the user's home directory by tkinter when the -E flag is passed to Python.
Patch by Zachary Ware.

- change references from configure.in to configure.ac

in the hash table internal to the pyexpat module's copy of the expat
library to avoid a denial of service due to hash collisions.
Patch by David Malcolm with some modifications by the expat project.

Remove setting hash seed to regrtest's random seed and re-execv()ing: this doesn't preserve Python flags and fails from a temp directory.

in order to make algorithmic complexity attacks on (e.g.) web apps much more complicated.

The environment variable PYTHONHASHSEED and the new command line flag -R control this
behavior.

upon malformed POST request.

Also remove an extra docstring.

Patch by Andreas Stührk.

the garbage collector while the Heap lock is held.