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)