Issue #11223: Add threading._info() function providing informations about the
thread implementation.

Skip test_lock_acquire_interruption() and test_rlock_acquire_interruption() of
test_threadsignals if a thread lock is implemented using a POSIX mutex and a
POSIX condition variable. A POSIX condition variable cannot be interrupted by a
signal (e.g. on Linux, the futex system call is restarted).
diff --git a/Lib/threading.py b/Lib/threading.py
index cb09afa..eb3cb62 100644
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -19,7 +19,7 @@
 
 __all__ = ['active_count', 'Condition', 'current_thread', 'enumerate', 'Event',
            'Lock', 'RLock', 'Semaphore', 'BoundedSemaphore', 'Thread', 'Barrier',
-           'Timer', 'setprofile', 'settrace', 'local', 'stack_size']
+           'Timer', 'setprofile', 'settrace', 'local', 'stack_size', '_info']
 
 # Rename some stuff so "from threading import *" is safe
 _start_new_thread = _thread.start_new_thread
@@ -31,6 +31,7 @@
 except AttributeError:
     _CRLock = None
 TIMEOUT_MAX = _thread.TIMEOUT_MAX
+_info = _thread.info
 del _thread