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.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        datatype.sgml (r1.257 -> r1.258)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/datatype.sgml?r1=1.257&r2=1.258)
        func.sgml (r1.532 -> r1.533)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml?r1=1.532&r2=1.533)
        monitoring.sgml (r1.85 -> r1.86)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/monitoring.sgml?r1=1.85&r2=1.86)
        plperl.sgml (r2.88 -> r2.89)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/plperl.sgml?r1=2.88&r2=2.89)
        sources.sgml (r2.37 -> r2.38)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/sources.sgml?r1=2.37&r2=2.38)
        xml2.sgml (r1.11 -> r1.12)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/xml2.sgml?r1=1.11&r2=1.12)