pgsql: More minor updates and copy-editing.

Log Message:
-----------
More minor updates and copy-editing.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        plhandler.sgml (r1.2 -> r1.3)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/plhandler.sgml.diff?r1=1.2&r2=1.3)
        plperl.sgml (r2.34 -> r2.35)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/plperl.sgml.diff?r1=2.34&r2=2.35)
        plpgsql.sgml (r1.53 -> r1.54)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/plpgsql.sgml.diff?r1=1.53&r2=1.54)
        plpython.sgml (r1.25 -> r1.26)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/plpython.sgml.diff?r1=1.25&r2=1.26)
        pltcl.sgml (r2.32 -> r2.33)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/pltcl.sgml.diff?r1=2.32&r2=2.33)
        spi.sgml (r1.36 -> r1.37)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/spi.sgml.diff?r1=1.36&r2=1.37)
        xfunc.sgml (r1.91 -> r1.92)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/xfunc.sgml.diff?r1=1.91&r2=1.92)
        xplang.sgml (r1.27 -> r1.28)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/xplang.sgml.diff?r1=1.27&r2=1.28)