Treat values passed on the command line as floats instead of longs.
This allows you to specify fractional percentages (and fractional
absolute values, too, though they’ll just be rounded down, so they’re
not particularly useful).

Report the display brightness as a percentage with two decimal places
rather than zero. To ensure backward compatibility in machine-readable
mode, report the high-precision percentage in a new field rather than
replacing the existing field. This does cause some redundancy in the
output, but that’s better than breaking scripts that assume the 4th
field is an integer followed by “%”.

Closes: Hummer12007#50