NAME:
     mag2flx
 PURPOSE: (one line)
     Convert from magnitudes to flux units with errors.
 DESCRIPTION:
 CATEGORY:
     Astronomy
 CALLING SEQUENCE:
     mag2flx,mag,magerr,flux,fluxerr
 INPUTS:
     mag    - Magnitudes.
     magerr - Uncertainties on the magnitudes.
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
     ZEROPT  - Magnitude that corresponds to a flux of 1. (default=0)
 OUTPUTS:
     flux    - Flux values for the magnitudes.
     fluxerr - Uncertainties on the fluxes.
 KEYWORD OUTPUT PARAMETERS:
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
 PROCEDURE:
 MODIFICATION HISTORY: