Remove SEP_CHAR, replace with / or '/' as appropriate.

src/backend/access/transam/xlog.c

src/backend/catalog/catalog.c

src/backend/postmaster/postmaster.c

src/backend/storage/file/fd.c

src/backend/utils/cache/relcache.c

src/backend/utils/error/elog.c

src/backend/utils/misc/database.c

src/bin/pg_dump/pg_dump.c

src/bin/psql/startup.c

src/include/c.h