Prevent output of repeated structure factors from list 3 into CIF. L3 is keyed on element name and gives scattering factor, so repeats will be ignored anyway. The need for this change is that repeated scattering factors (even with the right values) cause misleading errors in IUCr's checkCIF.
Change test output precision for regression tests. With GCC10 compilers some results are slightly more variable than previous versions (still within expected errors).