pgsql: Make pg_dump and friends consistently report both the filename

Log Message:
-----------
Make pg_dump and friends consistently report both the filename and the
errno string when complaining of fopen failures. Per gripe from Bob
Pawley, it's not always instantly obvious to the user which name we
tried to open.

Modified Files:
--------------
pgsql/src/bin/pg_dump:
pg_backup_archiver.c (r1.147 -> r1.148)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_archiver.c?r1=1.147&r2=1.148)
pg_backup_custom.c (r1.39 -> r1.40)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_custom.c?r1=1.39&r2=1.40)
pg_backup_files.c (r1.33 -> r1.34)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_files.c?r1=1.33&r2=1.34)
pg_backup_tar.c (r1.60 -> r1.61)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_tar.c?r1=1.60&r2=1.61)
pg_dumpall.c (r1.93 -> r1.94)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_dumpall.c?r1=1.93&r2=1.94)