totally rewrote the async signal, notification and oplock notification

handling in Samba. This was needed due to several limitations and
races in the previous code - as a side effect the new code is much
cleaner :)

in summary:

- changed sys_select() to avoid a signal/select race condition. It is a
  rare race but once we have signals doing notification and oplocks it
  is important.

- changed our main processing loop to take advantage of the new
  sys_select semantics

- split the notify code into implementaion dependent and general
  parts. Added the following structure that defines an implementation:

struct cnotify_fns {
	void * (*register_notify)(connection_struct *conn, char *path, uint32 flags);
	BOOL (*check_notify)(connection_struct *conn, uint16 vuid, char *path, uint32 flags, void *data, time_t t);
	void (*remove_notify)(void *data);
};


then I wrote two implementations, one using hash/poll (like our old
code) and the other using the new Linux kernel change notify. It
should be easy to add other change notify implementations by creating
a sructure of the above type.

- fixed a bug in change notify where we were returning the wrong error
  code.

- rewrote the core change notify code to be much simpler

- moved to real-time signals for leases and change notify

Amazingly, it all seems to work. I was very surprised!

source/smbd/oplock_irix.c

@@ -218,16 +218,16 @@ static BOOL irix_kernel_oplock_parse(char *msg_start, int msg_len, SMB_INO_T *in
 {
 	/* Ensure that the msg length is correct. */
 	if(msg_len != KERNEL_OPLOCK_BREAK_MSG_LEN) {
-		DEBUG(0,("process_local_message: incorrect length for KERNEL_OPLOCK_BREAK_CMD (was %d, \
-should be %d).\n", msg_len, KERNEL_OPLOCK_BREAK_MSG_LEN));
+		DEBUG(0,("incorrect length for KERNEL_OPLOCK_BREAK_CMD (was %d, should be %d).\n", 
+			 msg_len, KERNEL_OPLOCK_BREAK_MSG_LEN));
 		return False;
 	}
 
         memcpy((char *)inode, msg_start+KERNEL_OPLOCK_BREAK_INODE_OFFSET, sizeof(*inode));
         memcpy((char *)dev, msg_start+KERNEL_OPLOCK_BREAK_DEV_OFFSET, sizeof(*dev));
 
-        DEBUG(5,("process_local_message: kernel oplock break request for \
-file dev = %x, inode = %.0f\n", (unsigned int)*dev, (double)*inode));
+        DEBUG(5,("kernel oplock break request for file dev = %x, inode = %.0f\n", 
+		 (unsigned int)*dev, (double)*inode));
 
 	return True;
 }