Assert that wrapper_handler()'s argument is within expected range.
pqsignal() already does a similar check, but strange Valgrind
reports have us wondering if wrapper_handler() is somehow getting
called with an invalid signal number.
Reported-by: Tomas Vondra <tomas@vondra.me>
Suggested-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/
ace01111-f9ac-4f61-b1b1-
8e9379415444%40vondra.me
Backpatch-through: 17