Description: Set the current icon file
Mapped Command: SET ICON
FUNCTION __SetIcon(iconfile)
   if iconfile == NIL                            // if no file name was passed
      loadicon("")                               // clear the icon file in dGE
      _icnfile_ := ""                            // reset the static variable
   else                                          // otherwise...
      loadicon(_dgepath_+iconfile)               // load the file that was specified and set the static variable
      _icnfile_ := if(len(_dgepath_) > 0,_dgepath_ + iconfile,iconfile)
   endif                                         // if iconfile == nil
RETURN(_icnfile_)