Create separate ON INSERT and ON UPDATE triggers on tables with foreign

Create separate ON INSERT and ON UPDATE triggers on tables with foreign
keys, rather than a single trigger for both events. This should not change
functionality, but it is more consistent: previously, there were trigger
functions for both "check_insert" and "check_update", but the former was
used for both events.

Bump catalog version number (not strictly necessary, but best to be
cautious).