Thread: pgsql: Improve documentation/warning when --with-libxml is not used in

Log Message:
-----------
Improve documentation/warning when --with-libxml is not used in the
installation.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        datatype.sgml (r1.193 -> r1.194)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/datatype.sgml.diff?r1=1.193&r2=1.194)
        func.sgml (r1.374 -> r1.375)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml.diff?r1=1.374&r2=1.375)
    pgsql/src/backend/utils/adt:
        xml.c (r1.39 -> r1.40)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/xml.c.diff?r1=1.39&r2=1.40)