checkCIF procedure

PLAT710

 Torsion angles specified in the CIF are checked for the
 'linear variety' where one or both of the 1-2-3 and 2-3-4 bond 
 angles are close to 180 Deg. SHELXL97 will generate those 'torsions' for   
 molecules containing linear moieties (E.g. Metal-C=O).