- 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.

Just try to open files from the ZIP for reading, don't extract them to avoid
UnicodeEncodeError if the filename is not encodable to the filesystem encoding
(e.g. ASCII locale encoding).