pgsql: Tighten up the sanity checks in TypeCreate(): pass-by-value types

Log Message:
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Tighten up the sanity checks in TypeCreate(): pass-by-value types must have
a size that is one of the supported values, not just anything <= sizeof(Datum).
Cross-check the alignment specification against size as well.

Modified Files:
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    pgsql/src/backend/catalog:
        pg_type.c (r1.120 -> r1.121)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/pg_type.c?r1=1.120&r2=1.121)