Synopsis:

       db_flock(db_handle,on_or_off)

Arguments:

       db_handle - The database handle

       on_or_off - set to non-zero to set the file lock, or 0 to release the file lock

Description:  This function allows for an entire database table to be locked by setting the on_or_off argument to a non zero value.     Once a lock has been set then any other task that attempts to call the db_flock() function will fail to obtain the lock until the lock is released.

Returns:    Returns 0 or a negative error code.   It will return -24 if another task has already obtained the lock.