Add three new APIs: PyRun_AnyFileEx(), PyRun_SimpleFileEx(),

PyRun_FileEx().  These are the same as their non-Ex counterparts but
have an extra argument, a flag telling them to close the file when
done.

Then this is used by Py_Main() and execfile() to close the file after
it is parsed but before it is executed.

Adding APIs seems strange given the feature freeze but it's the only
way I see to close the bug report without incompatible changes.

[ Bug #110616 ] source file stays open after parsing is done (PR#209)

Python/bltinmodule.c

@@ -815,10 +815,7 @@ builtin_execfile(PyObject *self, PyObject *args)
 		PyErr_SetFromErrno(PyExc_IOError);
 		return NULL;
 	}
-	res = PyRun_File(fp, filename, Py_file_input, globals, locals);
-	Py_BEGIN_ALLOW_THREADS
-	fclose(fp);
-	Py_END_ALLOW_THREADS
+	res = PyRun_FileEx(fp, filename, Py_file_input, globals, locals, 1);
 	return res;
 }