who noticed that precession between B1950 to J2000 as done by KStars does not
coincide with the results given by SIMBAD (http://simbad.u-strasbg.fr/sim-fidl.pl).  M. Zotov has not opened yet a bug in bugs.kde.org, so I have no bug
number to refer to in this commit.

  The bug comes from the fact that conversion between coordinates in B1950
to J2000 (and viceversa) involves changing from (old) catalog FK4 to FK5,
and a simple precesion, as done by KStars is not enough.

To fix this bug I have used the following reference:
Smith, C. A.; Kaplan, G. H.; Hughes, J. A.; Seidelmann, P. K.; Yallop,
B. D.; Hohenkerk, C. Y.
Astronomical Journal, vol. 97, Jan. 1989, p. 265-279

The conversion between the FK4 catalog and the FK5 catalog requires 4 steps:
 - Drop E-Terms in B1950 coordinates. In the past, the mean places of
   stars published in the FK4 catalog included the contribution to the
   aberration due to the ellipticity of the orbit of...