pgsql: Better descriptions in pg_get_keywords(), consistent with the

Log Message:
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Better descriptions in pg_get_keywords(), consistent with the documentation
appendix on key words.  catdesc was originally intended as computer-readable,
but since we ended up adding catcode, we can have more elaborate descriptions.

Modified Files:
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    pgsql/src/backend/utils/adt:
        misc.c (r1.65 -> r1.66)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/misc.c?r1=1.65&r2=1.66)