even though it was useful. This would happen when the declaration was
duplicated (by inlining or by macro-expansion) and some but not all of
the copies were useful.

sentences and before the message.

Used by --interpret-error, --list-errors and --update-errors.

Introduced a ## marker for auto-generated comments.

Re-established rule_specific_token, which allows giving a better syntax error message when %% is missing.