Update intro comment for parser data scripts.
# * keywords: The keyword table holds names that are important keywords, such as
# if, for, while, and so on.
#
+# * expression dispatch: This table maps from a token to an expression handler.
+#
+# * keyword dispatch: This table maps from a key id to a keyword handler.
+#
+# * docblock verifier: This table is used to determine if a key id is allowed to
+# have a docblock.
+
import (finish_file,
open_file,
