pgsql: In pg_upgrade, don't copy visibility map files from clusters tha

In pg_upgrade, don't copy visibility map files from clusters that did not
have crash-safe visibility maps to clusters that expect crash-safety.

Request from Robert Haas.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/00a7c9014a8fbb7388a807daeba3e0a85b49a747

Modified Files
--------------
contrib/pg_upgrade/pg_upgrade.h | 6 ++++++
contrib/pg_upgrade/relfilenode.c | 18 ++++++++++++++++--
2 files changed, 22 insertions(+), 2 deletions(-)