SYSTEM FLOCK SUPPORT DEFINES

   d_fcntl_can_lock
      From d_fcntl_can_lock.U:
         This variable conditionally defines the FCNTL_CAN_LOCK symbol
         and indicates whether file locking with fcntl() works.

   d_flock
      From d_flock.U:
         This variable conditionally defines HAS_FLOCK if flock() is
         available to do file locking.

   d_lockf
      From d_lockf.U:
         This variable conditionally defines HAS_LOCKF if lockf() is
         available to do file locking.

         /FLOCKING CONSTANTS/

            classic values for these constants are as listed,
            but this can vary from system to system
               LOCK_EX 2
               LOCK_UN 8
               LOCK_NB 4
               LOCK_SH 1