Issue 10484 - Incorporate improvements to CGI module - Suggested by Glenn Linderman. Refactor code and tests

This avoids crashing the server loop when a signal is received.
Patch by Jerzy Kozera.

Issue #14505: Fix file descriptor leak when deallocating file objects created with PyFile_FromString().

Patch by Suman Saha.

Without this fix, both 2.7 and 3.x would always point to the "current"
docs...which means that before this fix python 3.2 'help' pointed to the 2.7
tutorial, and without this fix when we switch over to the 3.x docs being
current, 2.7 would have pointed to the python3 tutorial.

Patch by Sandro Tosi.

Added a new crasher that targets mutating the underlying storage of a buffer.  All work done by Armin Rigo.