pgsql: Fix case of pg_dump -Fc to an unseekable file (such as a pipe).

Fix case of pg_dump -Fc to an unseekable file (such as a pipe).

This was accidentally broken in commits cfa1b4a711/5e8e794e3b.
It saves a line or so to call ftello unconditionally in _CloseArchive,
but we have to expect that it might fail if we're not in hasSeek mode.
Per report from Bernd Helmle.

In passing, improve _getFilePos to print an appropriate message if
ftello fails unexpectedly, rather than just a vague complaint about
"ftell mismatch".

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/e03485ae8a2025d5deea291ebb24412229cc2fe5

Modified Files
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src/bin/pg_dump/pg_backup_custom.c |   22 +++++++++++++---------
1 file changed, 13 insertions(+), 9 deletions(-)