make: remove more distributed mode code

*** 129,140 ****
          Boolean                 make_refd;
  };
  
  typedef enum {
          serial_mode,
!         parallel_mode,
!         distributed_mode
  } DMake_mode;
  
  typedef enum {
          txt1_mode,
          txt2_mode,
--- 129,139 ----
          Boolean                 make_refd;
  };
  
  typedef enum {
          serial_mode,
!         parallel_mode
  } DMake_mode;
  
  typedef enum {
          txt1_mode,
          txt2_mode,