Warningfix knut

Warningsfixes by Knut.
Probably just to please the compiler or some static check.
As you say, 0 is representable. Epsilon is e.g. about 2^-52 (64bit) while the next largest number larger than 0 is about 2^-1022.
Still, using the (arbitrary) epsilon() could make sense in some cases if one assumes some small floating point errors (but not in this case :). 
Question is what to do with such warnings?