Bugs: mkarf

Users trying to run this tool with old versions of data products, those created with ASCDSVER less than version 8.4.2, may see warnings like

FITSIO status = 202: keyword not found in header
*** ERROR: *** Unable to get the value of `SUM_2X2' in /data/acisf04425_000N003_evt1.fits

Users should reprocess their data or use the r4_header_update script.

The comments and units of the output ARF file has some keyword and column that do not follow the standards (eg "sec" instead of "s" for seconds). The data values and keyword/column names are correct.