UTXX: meta.hpp: upper_power: added special case N=0 (the result is 0, exponent=-oo)
UTXX: meta.hpp: upper_power: added special case N=0 (the result is 0, exponent=-oo)

saleyn/utxx,saleyn/utxx,saleyn/utxx,saleyn/utxx,saleyn/utxx