[Bug c++/96185] Enhancement: Please add a builtin to count bindings in [dcl.struct.bind]

[wjwray at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96185

--- Comment #9 from Will Wray <wjwray at gmail dot com> ---
An earlier draft had __builtin_tuple_size as the magic behind the P2141
proposed std::tuple_size automagic generalization to Case 3 class types.

There was opposition to that name because it specifically doesn't apply
to tuples so I left the naming open, suggesting __builtin_binding_count
(and, so, requiring consensus on naming for portability...)