pgsql: Use the right type OID after creating a shell type

Use the right type OID after creating a shell type

Commit a2e35b53c39b2a neglected to update the type OID to use further
down in DefineType when TypeShellMake was changed to return
ObjectAddress instead of OID (it got it right in DefineRange, however.)
This resulted in an internal error message being issued when looking up
I/O functions.

Author: Michael Paquier

Also add Asserts() to a couple of other places to ensure that the type
OID being used is as expected.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/50a16e30ebd76e70fc76abb2c8f0cd1e71deac41

Modified Files
--------------
src/backend/commands/typecmds.c           |    4 +++-
src/test/regress/expected/create_type.out |    6 ++++++
src/test/regress/sql/create_type.sql      |    6 ++++++
3 files changed, 15 insertions(+), 1 deletion(-)