Issue #2377: Make importlib the implementation of __import__().

importlib._bootstrap is now frozen into Python/importlib.h and stored
as _frozen_importlib in sys.modules. Py_Initialize() loads the frozen
code along with sys and imp and then uses _frozen_importlib._install()
to set builtins.__import__() w/ _frozen_importlib.__import__().

Python/importdl.c

@@ -106,10 +106,6 @@ _PyImport_LoadDynamicModule(PyObject *name, PyObject *path, FILE *fp)
 
     if (_PyImport_FixupExtensionObject(m, name, path) < 0)
         goto error;
-    if (Py_VerboseFlag)
-        PySys_FormatStderr(
-            "import %U # dynamically loaded from %R\n",
-            name, path);
     Py_DECREF(nameascii);
     return m;