message: half.h: added unary negation operator
diff: @@ -44,6 +44,8 @@ struct half {
  half operator*(half h) const { return half(float(*this) * float(h)); }
  half operator/(half h) const { return half(float(*this) / float(h)); }
  + half operator-() const { return half(-float(*this)); }
  +
  ENOKI_IF_SCALAR friend half operator+(Value val, half h) { return half(val) + h; }
  ENOKI_IF_SCALAR friend half operator-(Value val, half h) { return half(val) - h; }
  ENOKI_IF_SCALAR friend half operator*(Value val, half h) { return half(val) * h; }
  