int LastBit() const
The LastBit method returns the index of the last bit, i.e.
the set bit with the highest index, in the OEBitVector. Bit
position indices are numbered from zero, and have a maximum of
OEBitVector::GetSize()-1. If the OEBitVector has no bits set,
i.e. OEBitVector::IsEmpty returns true, this method return
will return the value -1.