pgsql: pg_upgrade: adjust umask() calls

pg_upgrade: adjust umask() calls
Since pg_upgrade -j on Windows uses threads, calling umask()
before/after opening a file via fopen_priv() is no longer possible, so
set umask() as we enter the thread-creating loop, and reset it on exit.
Also adjust internal fopen_priv() calls to just use fopen().
Backpatch to 9.3beta.

Branch
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REL9_3_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/830d0e0edd73c015ca07423c402a3b1f79118d8f

Modified Files
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contrib/pg_upgrade/dump.c | 10 ++++++++++
contrib/pg_upgrade/exec.c | 11 +++--------
2 files changed, 13 insertions(+), 8 deletions(-)