pgsql: Fix a number of syntax errors in contrib modules' uninstall

Log Message:
-----------
Fix a number of syntax errors in contrib modules' uninstall scripts.
Most of the changes add the mandatory USING clause to DROP OPERATOR
CLASS statements.  DROP TYPE is now DROP TYPE CASCADE; without
CASCADE a DROP TYPE fails due to the circular dependency on the
type's I/O functions.  The DROP FUNCTION statements for the I/O
functions have been removed, as DROP TYPE CASCADE removes them
automatically. Patch from Michael Fuhr.

Modified Files:
--------------
    pgsql/contrib/btree_gist:
        uninstall_btree_gist.sql (r1.1 -> r1.2)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/btree_gist/uninstall_btree_gist.sql.diff?r1=1.1&r2=1.2)
    pgsql/contrib/chkpass:
        uninstall_chkpass.sql (r1.1 -> r1.2)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/chkpass/uninstall_chkpass.sql.diff?r1=1.1&r2=1.2)
    pgsql/contrib/cube:
        uninstall_cube.sql (r1.1 -> r1.2)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/cube/uninstall_cube.sql.diff?r1=1.1&r2=1.2)
    pgsql/contrib/dblink:
        uninstall_dblink.sql (r1.1 -> r1.2)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/dblink/uninstall_dblink.sql.diff?r1=1.1&r2=1.2)
    pgsql/contrib/intarray:
        uninstall__int.sql (r1.1 -> r1.2)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/intarray/uninstall__int.sql.diff?r1=1.1&r2=1.2)
    pgsql/contrib/isbn_issn:
        uninstall_isbn_issn.sql (r1.1 -> r1.2)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/isbn_issn/uninstall_isbn_issn.sql.diff?r1=1.1&r2=1.2)
    pgsql/contrib/ltree:
        uninstall_ltree.sql (r1.1 -> r1.2)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/ltree/uninstall_ltree.sql.diff?r1=1.1&r2=1.2)
    pgsql/contrib/pg_trgm:
        uninstall_pg_trgm.sql (r1.1 -> r1.2)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pg_trgm/uninstall_pg_trgm.sql.diff?r1=1.1&r2=1.2)
    pgsql/contrib/seg:
        uninstall_seg.sql (r1.1 -> r1.2)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/seg/uninstall_seg.sql.diff?r1=1.1&r2=1.2)