Spurious wakeups trigger re-registration. Also, in some cases, the msg/space available listeners were not being deregistered.  Also renamed Cell.msg to Cell.message, to visually distinguish between local vars and fields by the same name.

	modified:   Cell.java
	modified:   Mailbox.java
	modified:   Task.java
Removed debug statement
	modified:   src/kilim/Cell.java