checkViewTupleDesc() didn't get the memo that it should verify
same attcollation along with same type/typmod. (A quick scan
did not find other similar oversights.)
Per bug #17404 from Pierre-Aurélien Georges. On another day
I might've back-patched this, but today I'm feeling paranoid
about unnecessary behavioral changes in back branches.
Discussion: https://postgr.es/m/17404-8a4a270ef30a6709@postgresql.org