Fix lo_export usage in example programs.
Fix lo_export usage in example programs.

lo_export returns -1, not zero, on failure.

postmind-net/postgres-xl,postmind-net/postgres-xl,arcivanov/postgres-xl,snaga/postgres-xl,snaga/postgres-xl,arcivanov/postgres-xl,snaga/postgres-xl,kmjungersen/PostgresXL,kmjungersen/PostgresXL,postmind-net/postgres-xl,postmind-net/postgres-xl,arcivanov/postgres-xl,postmind-net/postgres-xl,snaga/postgres-xl,arcivanov/postgres-xl,snaga/postgres-xl,kmjungersen/PostgresXL,kmjungersen/PostgresXL,arcivanov/postgres-xl,kmjungersen/PostgresXL,arcivanov/postgres-xl