Re: [C++ Patch] Small SFINAE-related clean up

OK. Jason

[C++ Patch] Small SFINAE-related clean up

Hi, I believe that, as a general rule, a function taking a tsubst_flags_t complain parameter should propagate it, thus, in particular, call the *_sfinae variant of various helper functions we have got. The below fixes a few places where we weren't doing that (+ a couple of minor unrelated twe