pgsql: Remove pre-7.4 documentaiton mentions, now that 8.0 is the oldest

Log Message:
-----------
Remove pre-7.4 documentaiton mentions, now that 8.0 is the oldest
supported release.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        datatype.sgml (r1.242 -> r1.243)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/datatype.sgml?r1=1.242&r2=1.243)
        ddl.sgml (r1.88 -> r1.89)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ddl.sgml?r1=1.88&r2=1.89)
        libpq.sgml (r1.300 -> r1.301)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/libpq.sgml?r1=1.300&r2=1.301)
        protocol.sgml (r1.83 -> r1.84)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/protocol.sgml?r1=1.83&r2=1.84)
        rules.sgml (r1.53 -> r1.54)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/rules.sgml?r1=1.53&r2=1.54)
        xindex.sgml (r1.64 -> r1.65)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/xindex.sgml?r1=1.64&r2=1.65)