* even though the _Flags default to the corrected value, still correct   them in the ei_traits, so that they're guaranteed even if the user   specified his own non-default flags (like before).
* even though the _Flags default to the corrected value, still correct
  them in the ei_traits, so that they're guaranteed even if the user
  specified his own non-default flags (like before).

  Measured to not make compilation any slower.

robustrobotics/eigen,robustrobotics/eigen,robustrobotics/eigen,robustrobotics/eigen