New HeapTuple structure/interface.

src/backend/Makefile

src/backend/access/common/heaptuple.c

src/backend/access/common/heapvalid.c

src/backend/access/common/printtup.c

src/backend/access/common/tupdesc.c

src/backend/access/gist/gist.c

src/backend/access/hash/hash.c

src/backend/access/heap/heapam.c

src/backend/access/heap/hio.c

src/backend/access/nbtree/nbtinsert.c

src/backend/access/nbtree/nbtree.c

src/backend/access/rtree/rtree.c

src/backend/bootstrap/bootstrap.c

src/backend/catalog/aclchk.c

src/backend/catalog/heap.c

src/backend/catalog/index.c

src/backend/catalog/indexing.c

src/backend/catalog/pg_aggregate.c

src/backend/catalog/pg_operator.c

src/backend/catalog/pg_proc.c