Allow CREATE OR REPLACE VIEW to add columns to the _end_ of the view.

doc/src/sgml/ref/create_view.sgml

src/backend/commands/tablecmds.c

src/backend/commands/view.c

src/backend/parser/parse_utilcmd.c

src/include/nodes/parsenodes.h

src/test/regress/expected/create_view.out

src/test/regress/sql/create_view.sql