pgsql: Add strerror to pg_dump error messages where missing.

Log Message:
-----------
Add strerror to pg_dump error messages where missing.

Modified Files:
--------------
pgsql/src/bin/pg_dump:
common.c (r1.89 -> r1.90)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/common.c.diff?r1=1.89&r2=1.90)
pg_backup_archiver.c (r1.127 -> r1.128)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_archiver.c.diff?r1=1.127&r2=1.128)
pg_backup_custom.c (r1.33 -> r1.34)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_custom.c.diff?r1=1.33&r2=1.34)
pg_backup_files.c (r1.27 -> r1.28)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_files.c.diff?r1=1.27&r2=1.28)
pg_backup_tar.c (r1.50 -> r1.51)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_tar.c.diff?r1=1.50&r2=1.51)
pg_dumpall.c (r1.74 -> r1.75)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_dumpall.c.diff?r1=1.74&r2=1.75)