pgsql: Minor SGML style police work.

Log Message:
-----------
Minor SGML style police work.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        ddl.sgml (r1.54 -> r1.55)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ddl.sgml.diff?r1=1.54&r2=1.55)
        dml.sgml (r1.12 -> r1.13)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/dml.sgml.diff?r1=1.12&r2=1.13)
        plpgsql.sgml (r1.86 -> r1.87)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/plpgsql.sgml.diff?r1=1.86&r2=1.87)
        queries.sgml (r1.34 -> r1.35)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/queries.sgml.diff?r1=1.34&r2=1.35)
    pgsql/doc/src/sgml/ref:
        alter_function.sgml (r1.10 -> r1.11)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/alter_function.sgml.diff?r1=1.10&r2=1.11)