pgsql: Turn the -i/--ignore-version options of pg_dump and pg_dumpall

Log Message:
-----------
Turn the -i/--ignore-version options of pg_dump and pg_dumpall into no-ops:
the server version check is now always enforced.  Relax the version check to
allow a server that is of pg_dump's own major version but a later minor
version; this is the only case that -i was at all safe to use in.

pg_restore already enforced only a very weak version check, so this is
really just a documentation change for it.

Per discussion.

Modified Files:
--------------
    pgsql/doc/src/sgml/ref:
        pg_dump.sgml (r1.101 -> r1.102)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/pg_dump.sgml?r1=1.101&r2=1.102)
        pg_dumpall.sgml (r1.71 -> r1.72)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/pg_dumpall.sgml?r1=1.71&r2=1.72)
        pg_restore.sgml (r1.74 -> r1.75)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/pg_restore.sgml?r1=1.74&r2=1.75)
    pgsql/src/bin/pg_dump:
        pg_backup.h (r1.46 -> r1.47)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup.h?r1=1.46&r2=1.47)
        pg_backup_archiver.c (r1.153 -> r1.154)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_archiver.c?r1=1.153&r2=1.154)
        pg_backup_db.c (r1.78 -> r1.79)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_db.c?r1=1.78&r2=1.79)
        pg_dump.c (r1.486 -> r1.487)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_dump.c?r1=1.486&r2=1.487)
        pg_dumpall.c (r1.103 -> r1.104)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_dumpall.c?r1=1.103&r2=1.104)
        pg_restore.c (r1.87 -> r1.88)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_restore.c?r1=1.87&r2=1.88)