pgsql: Reject change of output-column collation in CREATE OR REPLACE VI

Reject change of output-column collation in CREATE OR REPLACE VIEW.

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

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/2523928b285b06242e0c669fadfc76d73bafdd66

Modified Files
--------------
src/backend/commands/view.c               | 20 ++++++++++++++++--
src/test/regress/expected/create_view.out | 34 +++++++++++++++++++------------
src/test/regress/sql/create_view.sql      | 25 +++++++++++++++--------
3 files changed, 56 insertions(+), 23 deletions(-)