Thread: pgsql: Add links to documentation sections in 9.0 release notes.

Log Message:
-----------
Add links to documentation sections in 9.0 release notes.

Also update tagging instructions, and add id tags to a few documentation
sections.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        release-9.0.sgml (r2.5 -> r2.6)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/release-9.0.sgml?r1=2.5&r2=2.6)
        release.sgml (r1.636 -> r1.637)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/release.sgml?r1=1.636&r2=1.637)
        runtime.sgml (r1.432 -> r1.433)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/runtime.sgml?r1=1.432&r2=1.433)
    pgsql/doc/src/sgml/ref:
        psql-ref.sgml (r1.242 -> r1.243)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/psql-ref.sgml?r1=1.242&r2=1.243)