bpo-35059: Add Py_STATIC_INLINE() macro (GH-10093)

* Add Py_STATIC_INLINE() macro to declare a "static inline" function.
  If the compiler supports it, try to always inline the function even if no
  optimization level was specified.
* Modify pydtrace.h to use Py_STATIC_INLINE() when WITH_DTRACE is
  not defined.
* Add an unit test on Py_DECREF() to make sure that
  _Py_NegativeRefcount() reports the correct filename.
diff --git a/Objects/object.c b/Objects/object.c
index 4597b12..8256071 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -200,14 +200,14 @@
 #ifdef Py_REF_DEBUG
 /* Log a fatal error; doesn't return. */
 void
-_Py_NegativeRefcount(const char *fname, int lineno, PyObject *op)
+_Py_NegativeRefcount(const char *filename, int lineno, PyObject *op)
 {
     char buf[300];
 
     PyOS_snprintf(buf, sizeof(buf),
                   "%s:%i object at %p has negative ref count "
                   "%" PY_FORMAT_SIZE_T "d",
-                  fname, lineno, op, op->ob_refcnt);
+                  filename, lineno, op, op->ob_refcnt);
     Py_FatalError(buf);
 }