THIS SUBROUTINE CONVERTS ICRS RIGHT ASCENSION AND DECLINATION
TO GALACTIC LONGITUDE AND LATITUDE. IT USES THE TRANSFORMATION
GIVEN IN THE HIPPARCOS AND TYCHO CATALOGUES, VOL. 1,
SECTION 1.5.3.
RA = ICRS RIGHT ASCENSION IN HOURS (IN)
DEC = ICRS DECLINATION IN DEGREES (IN)
GLON = GALACTIC LONGITUDE IN DEGREES (OUT)
GLAT = GALACTIC LATITUDE IN DEGREES (OUT)
Nodes of different colours represent the following:
Solid arrows point from a procedure to one which it calls. Dashed
arrows point from an interface to procedures which implement that interface.
This could include the module procedures in a generic interface or the
implementation in a submodule of an interface in a parent module.