It probably makes sense for the hook to get all the arguments that
check_special_symbol gets too, so it can check some details of the specific
symbol rather than just generically for known bits. Hmm, perhaps even just
having check_special_symbol do this would be OK too, though that might be
too coarse since it's used in several places. If it is a new hook, then
it might be better for it to get st_other & ~GELF_ST_VISIBILITY so that
the backend only has to check for the machine-specific bits instead of
also encoding the generic knowledge.