pgsql: Doc fixes: - remove excessive table cells - moving function

Log Message:
-----------
Doc fixes:

- remove excessive table cells
- moving function parameters into function tags rather than having
  them being considered separate
- add return type column on XML2 contrib module functions list and
  removing return types from function
- add table header to XML2 contrib parameter table

Thom Brown

Backpatch to 9.0.X.

Tags:
----
REL9_0_STABLE

Modified Files:
--------------
    pgsql/doc/src/sgml:
        datatype.sgml (r1.250.2.6 -> r1.250.2.7)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/datatype.sgml?r1=1.250.2.6&r2=1.250.2.7)
        func.sgml (r1.521.2.5 -> r1.521.2.6)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml?r1=1.521.2.5&r2=1.521.2.6)
        monitoring.sgml (r1.80.2.2 -> r1.80.2.3)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/monitoring.sgml?r1=1.80.2.2&r2=1.80.2.3)
        plperl.sgml (r2.86.2.2 -> r2.86.2.3)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/plperl.sgml?r1=2.86.2.2&r2=2.86.2.3)
        sources.sgml (r2.36 -> r2.36.2.1)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/sources.sgml?r1=2.36&r2=2.36.2.1)
        xml2.sgml (r1.7.14.4 -> r1.7.14.5)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/xml2.sgml?r1=1.7.14.4&r2=1.7.14.5)