Avoid index rebuild for no-rewrite ALTER TABLE .. ALTER TYPE.

doc/src/sgml/xindex.sgml

src/backend/bootstrap/bootparse.y

src/backend/catalog/heap.c

src/backend/catalog/index.c

src/backend/catalog/storage.c

src/backend/catalog/toasting.c

src/backend/commands/indexcmds.c

src/backend/commands/tablecmds.c

src/backend/nodes/copyfuncs.c

src/backend/nodes/equalfuncs.c

src/backend/nodes/outfuncs.c

src/backend/tcop/utility.c

src/backend/utils/cache/relcache.c

src/backend/utils/cache/relmapper.c

src/include/catalog/heap.h

src/include/catalog/index.h

src/include/catalog/storage.h

src/include/commands/defrem.h

src/include/nodes/parsenodes.h

src/include/utils/relcache.h