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__().
diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index f3dde11..a2f2e44 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -2344,9 +2344,9 @@
 #endif /* MS_WINDOWS */
 
 void
-_PyExc_Init(void)
+_PyExc_Init(PyObject *bltinmod)
 {
-    PyObject *bltinmod, *bdict;
+    PyObject *bdict;
 
     PRE_INIT(BaseException)
     PRE_INIT(Exception)
@@ -2414,9 +2414,6 @@
     PRE_INIT(ProcessLookupError);
     PRE_INIT(TimeoutError);
 
-    bltinmod = PyImport_ImportModule("builtins");
-    if (bltinmod == NULL)
-        Py_FatalError("exceptions bootstrapping error.");
     bdict = PyModule_GetDict(bltinmod);
     if (bdict == NULL)
         Py_FatalError("exceptions bootstrapping error.");
@@ -2546,7 +2543,6 @@
             Py_DECREF(args_tuple);
         }
     }
-    Py_DECREF(bltinmod);
 }
 
 void