pgsql: Minor pg_dump improvements

Minor pg_dump improvements

Improve pg_dump by checking results on various fgetc() calls which
previously were unchecked, ditto for ftello.  Also clean up a couple
of very minor memory leaks by waiting to allocate structures until
after the initial check(s).

Issues spotted by Coverity.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/cfa1b4a711dd03f824a9c3ab50911e61419d1eeb

Modified Files
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src/bin/pg_dump/pg_backup_archiver.c |   27 +++++++++++++++++++++------
src/bin/pg_dump/pg_backup_custom.c   |    5 ++++-
src/bin/pg_dump/pg_dump.c            |    8 ++++++--
3 files changed, 31 insertions(+), 9 deletions(-)