test_gdb.StackNavigationTests.test_pycfunction checks that the GDB integration can pick up calls to C-API functions. Currently it includes the comment:

> Tested function must not be defined with METH_NOARGS or METH_O,
> otherwise call_function() doesn't call PyCFunction_Call()

This is (now?) false; furthermore it looks like all builtin_function_or_method are discoverable.

As the code paths for various METH_* conventions are diverging due to optimizations, we should check they continue to be covered.