pgsql: Improve pg_upgrade error reporting if the bin or data directorie

Improve pg_upgrade error reporting if the bin or data directories do not
exist or are not directories.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/772a5f1e5b343d07e907ef7f36fa36d190d55912

Modified Files
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contrib/pg_upgrade/exec.c | 50 +++++++++++++++++++++++---------------------
1 files changed, 26 insertions(+), 24 deletions(-)