ISTM that it is kind of a regression, because logically this is about the scan state so it should be in the corresponding structure, and having two structures to pass the scan state is not an improvement...
I wasn't too happy with the extra param, either. Having moved the guts to conditional.c, I'm happy with that change and can move the stack head back to scan_state with a clear conscience.
So moving the conditional stack back into PsqlScanState has some side effects: conditional.[ch] have to move to the fe_utils/ dirs, and now pgbench, which does not use conditionals, would have to link to them. Is that a small price to pay for modularity and easier-to-find code? Or should I just tuck it back into psqlscan_int.[ch]?
