pgsql: Looks like we need #include <sys/stat.h> here on some platforms.

Log Message:
-----------
Looks like we need #include <sys/stat.h> here on some
platforms. Per buildfarm.

Modified Files:
--------------
pgsql/src/backend/utils/cache:
relmapper.c (r1.1 -> r1.2)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/cache/relmapper.c?r1=1.1&amp;r2=1.2)