pgsql: Rename several aliases for PLpgSQL_datum.dno to also be called

Log Message:
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Rename several aliases for PLpgSQL_datum.dno to also be called dno.
Hopefully this will forestall future confusion about their roles.

Jonah Harris

Modified Files:
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    pgsql/src/pl/plpgsql/src:
        gram.y (r1.115 -> r1.116)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpgsql/src/gram.y?r1=1.115&r2=1.116)
        pl_comp.c (r1.131 -> r1.132)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpgsql/src/pl_comp.c?r1=1.131&r2=1.132)
        pl_exec.c (r1.223 -> r1.224)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpgsql/src/pl_exec.c?r1=1.223&r2=1.224)
        pl_funcs.c (r1.73 -> r1.74)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpgsql/src/pl_funcs.c?r1=1.73&r2=1.74)
        plpgsql.h (r1.104 -> r1.105)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpgsql/src/plpgsql.h?r1=1.104&r2=1.105)