subrepos/binaryen: binaryen: Debug info handling for new EH try-catch…

… (#3496) (c74acc0baece1296ad58a0ff44119fb36d98d2c6)

We now have multiple catches in each try, and a possible catch-all.

This changes our "extra delimiter" storage to store either an "else"
(unchanged from before) or an arbitrary list of things - we use that
for catches.