Avoid conflicting signal registrations when run under mod_wsgi. Allows the use of `WSGIRestrictSignal Off` (LP #681853).

The locking here was only ever needed for the old `regex` module that was
originally used for this code, but that was replaced by the thread-safe `re`
some 10 years ago (see r20110, april 2001).

Use the cookie APIs or addHeader instead.

  order : tids were stored and retrieved as dictionary keys. 

in the proper order : tids were stored and retrieved as dictionary keys.