Обсуждение: pgsql: Fix some SGML-compiler warnings on -wxml mode.

Log Message:
-----------
Fix some SGML-compiler warnings on -wxml mode.

Modified Files:
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    pgsql/doc/src/sgml:
        advanced.sgml (r1.56 -> r1.57)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/advanced.sgml?r1=1.56&r2=1.57)
        catalogs.sgml (r2.193 -> r2.194)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/catalogs.sgml?r1=2.193&r2=2.194)
        installation.sgml (r1.318 -> r1.319)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/installation.sgml?r1=1.318&r2=1.319)
        plpgsql.sgml (r1.136 -> r1.137)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/plpgsql.sgml?r1=1.136&r2=1.137)
        syntax.sgml (r1.129 -> r1.130)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/syntax.sgml?r1=1.129&r2=1.130)