Remove unused #includes in *.c files.

src/backend/access/common/heaptuple.c

src/backend/access/common/indextuple.c

src/backend/access/common/indexvalid.c

src/backend/access/common/printtup.c

src/backend/access/common/scankey.c

src/backend/access/common/tupdesc.c

src/backend/access/gist/gist.c

src/backend/access/gist/gistget.c

src/backend/access/gist/gistscan.c

src/backend/access/hash/hash.c

src/backend/access/hash/hashfunc.c

src/backend/access/hash/hashinsert.c

src/backend/access/hash/hashovfl.c

src/backend/access/hash/hashpage.c

src/backend/access/hash/hashsearch.c

src/backend/access/hash/hashstrat.c

src/backend/access/hash/hashutil.c

src/backend/access/heap/heapam.c

src/backend/access/heap/hio.c

src/backend/access/heap/stats.c