BUGFIX in coordinates.f90/aberration_eq(), used for stars

* BUGFIX in coordinates.f90/aberration_eq(), used for stars:
  * left out time factor
Some cleaning and commenting
planets.f90/planet_position_la(): correct for parallax only if calc==5
sun.f90/sunpos_la(): slightly more accurate routines

* sun.f90/sunpos_la(): slightly more accurate routines:
  * better omg, dpsi, aber
    * doesn't make a big difference
  * odot is off by ~10" in Meeus, Example 25a.  Would need better L0 or C (or M?)