Fix redefinition of typedefs
Per buildfarm members sifaka and longfin, clang with
-Wtypedef-redefinition warns of duplicate typedefs unless building with
C11. Follow-up to
ee1b30f12.
Masahiko Sawada
Discussion: https://postgr.es/m/CANWCAZauSg%3DLUbBbXhpeQtBuPifmzQNTYS6O8NsoAPz1zL-Txg%40mail.gmail.com