NAME:
  logerror
 PURPOSE:
  Simplified error logging program.
 DESCRIPTION:

 CATEGORY:
  Miscellaneous
 CALLING SEQUENCE:
  logerror,file,msg
 INPUTS:
  file  - string containing file name of error log file
  msg   - string (scalar or array) to be written to log file
 OPTIONAL INPUT PARAMETERS:

 KEYWORD INPUT PARAMETERS:
  CLEARLOG - Flag, if set, causes log file to be cleared before writing.
               The default is that all messages are appended to the file.
               If the file doesn't already exist this flag has no effect.
  QUIET    - 0 - default, message printed to screen also, with CALLER tag.
             1 - nothing printed to screen
  CALLER   - Optional id string that identifies the calling program.
 OUTPUTS:

 KEYWORD OUTPUT PARAMETERS:

 COMMON BLOCKS:

 SIDE EFFECTS:

 RESTRICTIONS:

 PROCEDURE:

 MODIFICATION HISTORY:
  Written by Marc W. Buie, Lowell Observatory, 2000/09/12
  2001/04/18, MWB, changed systime call.