pgsql: Fix core dump in pg_dump --binary-upgrade on zero-column composi

Fix core dump in pg_dump --binary-upgrade on zero-column composite type.

This reverts nearly all of commit 28f6cab61ab8958b1a7dfb019724687d92722538
in favor of just using the typrelid we already have in pg_dump's TypeInfo
struct for the composite type. As coded, it'd crash if the composite type
had no attributes, since then the query would return no rows.

Back-patch to all supported versions. It seems to not really be a problem
in 9.0 because that version rejects the syntax "create type t as ()", but
we might as well keep the logic similar in all affected branches.

Report and fix by Rushabh Lathia.

Branch
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REL9_2_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/787e20bd4a33fd076cad1fd3ec58c644a14d8390

Modified Files
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src/bin/pg_dump/pg_dump.c | 12 +++---------
1 file changed, 3 insertions(+), 9 deletions(-)