Re-apply Darren's char2-16 removal code.

src/backend/access/common/tupdesc.c

src/backend/access/hash/hashfunc.c

src/backend/access/nbtree/nbtcompare.c

src/backend/access/transam/xid.c

src/backend/bootstrap/bootparse.y

src/backend/bootstrap/bootstrap.c

src/backend/commands/creatinh.c

src/backend/commands/dbcommands.c

src/backend/executor/execQual.c

src/backend/parser/parse_expr.c

src/backend/rewrite/rewriteRemove.c

src/backend/rewrite/rewriteSupport.c

src/backend/tcop/fastpath.c

src/backend/utils/adt/char.c

src/backend/utils/adt/like.c

src/backend/utils/adt/regexp.c

src/backend/utils/adt/regproc.c

src/backend/utils/cache/catcache.c

src/include/access/hash.h

src/include/catalog/pg_amop.h