pgsql: Fix up pg_dump to emit shell-type definitions at the proper time,

Log Message:
-----------
Fix up pg_dump to emit shell-type definitions at the proper time, to
make use of the recently added ability to create a shell type explicitly.

I also put in place some infrastructure to allow dump/no dump decisions
to be made separately for each database object, rather than the former
hardwired 'dump if in a dumpable schema' policy. This was needed anyway
for shell types so now seemed a convenient time to do it. The flexibility
isn't exposed to the user yet, but is ready for future extensions.

Modified Files:
--------------
pgsql/src/bin/pg_dump:
common.c (r1.87 -> r1.88)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/common.c.diff?r1=1.87&r2=1.88)
pg_dump.c (r1.430 -> r1.431)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_dump.c.diff?r1=1.430&r2=1.431)
pg_dump.h (r1.123 -> r1.124)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_dump.h.diff?r1=1.123&r2=1.124)
pg_dump_sort.c (r1.12 -> r1.13)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_dump_sort.c.diff?r1=1.12&r2=1.13)