I did some of the flags and assertions wrong. Thanks to Brad Beckmann
for pointing this out. I should have run the opt regressions instead
of the fast. I also screwed up some of the logical functions in the Flags
class.
In many cases it might be preferable to use bitset, but this object
allows the user more easily manipulate groups of flags because the
underlying type (e.g. uint64_t) is exposed.
