pgsql: Skip recently-added umask() call on Windows.

Skip recently-added umask() call on Windows.

Symbols S_IRWXG and S_IRWXO became available to Windows builds in commit
1319002e2ee166c06b38cdbc5e8508c7205fa115, so PostgreSQL 9.0 cannot use
them in platform-independent code.  Rewrite commit
24aed2124a5273e4cb543b06d4b7bb2c2ad5bf3c to not change Windows builds.
The new umask() call had no effect on Windows, anyway.  Per buildfarm.

Branch
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REL9_0_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/c69e7d5c78af946b22d46afc60823d20197ca3e3

Modified Files
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src/bin/pg_dump/pg_backup_tar.c |   27 ++++++++++++++-------------
1 file changed, 14 insertions(+), 13 deletions(-)