Make vararg combinators macros that add the sentinel
This is an idea for a possible enhancement. Feedback welcome!
Turn e.g. h_sequence(foo, bar, baz, NULL)
into h_sequence(foo, bar, baz)
which expands to h_sequence_(foo, bar, baz, NULL)
or somesuch.
Motivation: The sentinel arguments are a pain to read, to type, and easy to forget.