[babel_]

Testing with Jen's macro this was based on, and found that the always_inline was redundant under even -O1 (https://godbolt.org/z/qoh861Gch via the examples from N3488 as became the baseline for the TS for C2y, which has recently a new revision under N3687), so there's an interesting trade-off between visibly seeing the `defer` by not not-inlining within the macro under an -O0 or similar unoptimised build, since with the inlining they are unmarked in the disassembly. But, there's an interesting twist here, as "defer: the feature" is likely not going to be implemented as "defer: the macro", since compilers will have the keyword (just `defer` in TS25755, or something else that uses a header for sugared `defer`) and may see the obvious optimised rewrite as the straightforward way of implementing it in the first place (as some already have), meaning we can have the benefit of the optimised inline with the opportunity to also keep it clearly identifiable, even in unoptimised and debug builds, which would certainly be nice to have!