add optimization test

examples/optimization.l3

+(def byte-write (fun (c) (@byte-write c)))
+(def compose
+     (fun (f g)
+	  (fun (x) (f (g x)))))
+(def + (fun (x y) (@+ x y)))
+(def succ (fun (x) (+ x 1)))
+(def twice (fun (x) (+ x x)))
+(byte-write ((compose succ twice) 39))
+(byte-write ((compose succ succ) 73))
+(byte-write ((compose twice succ) 4))
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