NAME:
       close_all
 PURPOSE:
       closes any open files with nos 1 to 6
 CALLING SEQUENCE:
       close_all
 INPUTS:
      
 OPTIONAL INPUT KEYWORDS:
       
 OPTIONAL OUTPUT PARAMETERS:
       
 EXAMPLE:
      
 CALLED PROCEDURES:
       
 MODIFICATION HISTORY:
       09-Jan-2001  Original by Suzanne Aigrain

(See /home/xmmssc/soft/idl/pro/files/close_all.pro)