pgsql: Avoid C99-ism in pre-v12 branches.

Avoid C99-ism in pre-v12 branches. Per buildfarm (I need to figure out why my own compiler did not whine about this). Branch -- REL_10_STABLE Details --- https://git.postgresql.org/pg/commitdiff/a00dbfaeed4017bca695a3e77d0f6264ba94a4c1 Modified Files -- src/backend/catalog/i

pgsql: Avoid C99-ism in pre-v12 branches.

Avoid C99-ism in pre-v12 branches. Per buildfarm (I need to figure out why my own compiler did not whine about this). Branch -- REL_11_STABLE Details --- https://git.postgresql.org/pg/commitdiff/22b96f883fe2a454476b4d5fd69ee46b15889169 Modified Files -- src/backend/catalog/i