bpo-29464: Rename METH_FASTCALL to METH_FASTCALL|METH_KEYWORDS and make (#1955)

the bare METH_FASTCALL be used for functions with positional-only
parameters.
diff --git a/Python/clinic/_warnings.c.h b/Python/clinic/_warnings.c.h
index 550c73f..334f9d1 100644
--- a/Python/clinic/_warnings.c.h
+++ b/Python/clinic/_warnings.c.h
@@ -9,7 +9,7 @@
 "Issue a warning, or maybe ignore it or raise an exception.");
 
 #define WARNINGS_WARN_METHODDEF    \
-    {"warn", (PyCFunction)warnings_warn, METH_FASTCALL, warnings_warn__doc__},
+    {"warn", (PyCFunction)warnings_warn, METH_FASTCALL|METH_KEYWORDS, warnings_warn__doc__},
 
 static PyObject *
 warnings_warn_impl(PyObject *module, PyObject *message, PyObject *category,
@@ -35,4 +35,4 @@
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=acadf1788059034c input=a9049054013a1b77]*/
+/*[clinic end generated code: output=74b1a7d1ee41816d input=a9049054013a1b77]*/