moonpos_la(): verify whether data were read
BUGFIX in sun.f90/sunpos_la() affecting dec, az,alt of the Sun

* BUGFIX in sun.f90/sunpos_la() affecting dec, az,alt of the Sun:
  * typo with brackets
  * accuracy in equitorial and horizontal position was ~520" rather than ~11"
Updated low-accuracy Sun,Moon routines with proper topocentric coordinates

* Updated low-accuracy Sun,Moon routines with proper topocentric coordinates:
  * expensive (+15% CPU for Moon, +110% for Sun); computed only if calc>=6
  * convert l,b and ra,dec; compute az,alt from ra,dec
  * for calc=5, use cheap version for alt only

  * improved accuracy, mean+-stdev for 1000 random test positions:
    * Sun:  14+-7" -> 11+-7" (expensive and cheap alt)
    * Moon: 0.83+-0.14deg -> 22+-11" (cheap alt) -> 2.6+-1.8" (calc=6, nt=60)

  * added lst tot planpos (44)