Update the examples for the master (do and closure change).

Not sure in the msgsend example I replace spawn_with() with spawn(proc) because  spawn_with diseapear.
I didn't already understand what proc do. I'am investigating to have a better understanding.
Tests the examples and they work.

I remove the 
-#[link_args="-lzmq"]
-extern {}

because I suppose they arn't needed or I don't know the reason. I can put them back if you want.