pgsql: Report postmaster.pid file as empty if it is empty, rather than

Report postmaster.pid file as empty if it is empty, rather than
reporting in contains invalid data.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/3825963e7fbaa8dbc462d4f5286ff6149f4703dd

Modified Files
--------------
src/backend/utils/init/miscinit.c | 8 ++++++++
src/bin/pg_ctl/pg_ctl.c | 9 +++++++--
2 files changed, 15 insertions(+), 2 deletions(-)