pgsql: Truncate filenames in the leadning end in pg_basebackup verbose

Truncate filenames in the leadning end in pg_basebackup verbose output

When truncating at the end, like before, the output would often end up
just showing the path instead of the filename.

Also increase the length of the filename by 5, which still keeps us at
less than 80 characters in most outputs.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/d7e9ca7ff7efac8b15d4348fd9480c12ed560ae7

Modified Files
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src/bin/pg_basebackup/pg_basebackup.c |   24 ++++++++++++++++++------
1 files changed, 18 insertions(+), 6 deletions(-)