mtz2cif: use new items in _diffrn_refln
mtz2cif: use new items in _diffrn_refln

_diffrn_refln.pdbx_image_id and _diffrn_refln.pdbx_scan_angle from
https://github.com/wwpdb-dictionaries/mmcif_pdbx/pull/33

project-gemmi/gemmi,project-gemmi/gemmi,project-gemmi/gemmi,project-gemmi/gemmi