P3935 Wrong names for `fminum_mag`/`fmaximum_mag`

[eisenwave]

fminimum_mag_num suffixed names use wrong prefix: Under fminimum_mag_num, the suffixed versions read fmaximum_mag_numf and fmaximum_mag_numl — these should be fminimum_mag_numf and fminimum_mag_numl.