pgsql: Change the interpretation of the primary_key_attnums parameter of

Log Message:
-----------
Change the interpretation of the primary_key_attnums parameter of
dblink_build_sql_insert() and related functions.  Now the column numbers
are treated as logical not physical column numbers.  This will provide saner
behavior in the presence of dropped columns; furthermore, if we ever get
around to allowing rearrangement of logical column ordering, the original
definition would become nearly untenable from a usability standpoint.
Per recent discussion of dblink's handling of dropped columns.
Not back-patched for fear of breaking existing applications.

Modified Files:
--------------
    pgsql/contrib/dblink:
        dblink.c (r1.97 -> r1.98)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/dblink/dblink.c?r1=1.97&r2=1.98)
    pgsql/contrib/dblink/expected:
        dblink.out (r1.30 -> r1.31)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/dblink/expected/dblink.out?r1=1.30&r2=1.31)
    pgsql/contrib/dblink/sql:
        dblink.sql (r1.24 -> r1.25)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/dblink/sql/dblink.sql?r1=1.24&r2=1.25)
    pgsql/doc/src/sgml:
        dblink.sgml (r1.12 -> r1.13)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/dblink.sgml?r1=1.12&r2=1.13)