bpo-36842: Implement PEP 578 (GH-12613)

Adds sys.audit, sys.addaudithook, io.open_code, and associated C APIs.
diff --git a/Include/pydtrace.d b/Include/pydtrace.d
index a6a5e7e..5e6a626 100644
--- a/Include/pydtrace.d
+++ b/Include/pydtrace.d
@@ -12,6 +12,7 @@
     probe gc__done(long);
     probe import__find__load__start(const char *);
     probe import__find__load__done(const char *, int);
+    probe audit(const char *, void *);
 };
 
 #pragma D attributes Evolving/Evolving/Common provider python provider