This removes nested loops in PyEval_EvalCodeEx.

Issue 11758: increase xml.dom.minidom test coverage (contributed by mdorn, reviewed by Sandro Tosi).

Patch by Akira Kitada.

On FreeBSD6, pthread_kill() doesn't work on the main thread before the creation
of the first thread. Create therefore a dummy thread (no-op) a startup to
initialize the pthread library.

Add also a test for this use case, test written by Charles-François Natali.