pgsql: Fix SortTocFromFile() to cope with lines that are too long for i

Fix SortTocFromFile() to cope with lines that are too long for its buffer.

The original coding supposed that a dump TOC file could never contain lines
longer than 1K. The folly of that was exposed by a recent report from
Per-Olov Esgard. We only really need to see the first dozen or two bytes
of each line, since we're just trying to read off the numeric ID at the
start of the line; so there's no need for a particularly huge buffer.
What there is a need for is logic to not process continuation bufferloads.

Back-patch to all supported branches, since it's always been like this.

Branch
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REL8_2_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/00a922906073314f9ba000c933eb6d2308c0a162

Modified Files
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src/bin/pg_dump/pg_backup_archiver.c | 29 ++++++++++++++++++++++++-----
1 files changed, 24 insertions(+), 5 deletions(-)