(split from Astrognome)Added GswePlanetInfo.real_body field

It shows if the given astrological body's position can be calculated with
Swiss Ephemeris' swe_calc() function.

src/gswe-types.h

@@ -86,6 +86,10 @@ typedef enum {
  * @planet:          the planet ID
  * @sweph_id:        the planet ID according to the Swiss Ephemeris libarary
  *                   (or -1, if the planet has no such ID)
+ * @real_body:       TRUE if the planet is a "real" celestial body on the sky.
+ *                   Please note that this will be true for Dark Moon (Lilith).
+ *                   Everything that has a planet ID in Swiss Ephemeris is
+ *                   treated as a real celestial body.
  * @orb:             the planet's “personal” orb
  * @name:            the planet's name
  * @points:          the value this planet counts in the element/quality points
@@ -100,6 +104,7 @@ typedef enum {
 typedef struct {
     GswePlanet planet;
     gint sweph_id;
+    gboolean real_body;
     gdouble orb;
     gchar *name;
     gint points;