checkCIF procedure

PLAT990

 SQUEEZE jobs should as of the availability of SHELXL20xy be based on the   
 use of a CIF+FCF created in a SHELXL20xy refinement. Use the generated 
 _sq.ins, _sq.hkl and _.sq.fab files for follow-up SHELXL based refinement.  
 See A.L.Spek (2015) Acta Cryst. C71, 9-18.