Add zpbit and varbit data types from Adrian Joubert

src/backend/utils/adt/Makefile

src/backend/utils/adt/varbit.c

src/include/catalog/pg_operator.h

src/include/catalog/pg_proc.h

src/include/catalog/pg_type.h

src/include/utils/builtins.h

src/include/utils/varbit.h