pgsql: Fix the problem that creating a user-defined type named _foo,

Log Message:
-----------
Fix the problem that creating a user-defined type named _foo, followed by one
named foo, would work but the other ordering would not. If a user-specified
type or table name collides with an existing auto-generated array name, just
rename the array type out of the way by prepending more underscores. This
should not create any backward-compatibility issues, since the cases in which
this will happen would have failed outright in prior releases.

Also fix an oversight in the arrays-of-composites patch: ALTER TABLE RENAME
renamed the table's rowtype but not its array type.

Modified Files:
--------------
pgsql/doc/src/sgml/ref:
create_type.sgml (r1.70 -> r1.71)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/create_type.sgml.diff?r1=1.70&r2=1.71)
pgsql/src/backend/catalog:
heap.c (r1.319 -> r1.320)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/heap.c.diff?r1=1.319&r2=1.320)
pg_type.c (r1.112 -> r1.113)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/pg_type.c.diff?r1=1.112&r2=1.113)
pgsql/src/backend/commands:
tablecmds.c (r1.221 -> r1.222)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/tablecmds.c.diff?r1=1.221&r2=1.222)
typecmds.c (r1.103 -> r1.104)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/typecmds.c.diff?r1=1.103&r2=1.104)
pgsql/src/include/catalog:
pg_type.h (r1.183 -> r1.184)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_type.h.diff?r1=1.183&r2=1.184)
pgsql/src/test/regress/expected:
arrays.out (r1.32 -> r1.33)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/arrays.out.diff?r1=1.32&r2=1.33)
pgsql/src/test/regress/sql:
arrays.sql (r1.25 -> r1.26)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/arrays.sql.diff?r1=1.25&r2=1.26)