bpo-34271: Add ssl debugging helpers (GH-10031)

The ssl module now can dump key material to a keylog file and trace TLS
protocol messages with a tracing callback. The default and stdlib
contexts also support SSLKEYLOGFILE env var.

The msg_callback and related enums are private members. The feature
is designed for internal debugging and not for end users.

Signed-off-by: Christian Heimes <christian@python.org>

setup.py

@@ -2178,11 +2178,13 @@ class PyBuildExt(build_ext):
             ssl_incs.extend(krb5_h)
 
         if config_vars.get("HAVE_X509_VERIFY_PARAM_SET1_HOST"):
-            self.add(Extension('_ssl', ['_ssl.c'],
-                               include_dirs=openssl_includes,
-                               library_dirs=openssl_libdirs,
-                               libraries=openssl_libs,
-                               depends=['socketmodule.h']))
+            self.add(Extension(
+                '_ssl', ['_ssl.c'],
+                include_dirs=openssl_includes,
+                library_dirs=openssl_libdirs,
+                libraries=openssl_libs,
+                depends=['socketmodule.h', '_ssl/debughelpers.c'])
+            )
         else:
             self.missing.append('_ssl')