Add btree indexing of boolean values

src/backend/access/nbtree/nbtcompare.c

src/backend/utils/adt/bool.c

src/include/catalog/pg_amop.h

src/include/catalog/pg_amproc.h

src/include/catalog/pg_opclass.h

src/include/catalog/pg_operator.h

src/include/catalog/pg_proc.h

src/include/utils/builtins.h