samples: add Terra samples

source: https://github.com/zdevito/terra/tree/master/tests

samples/Terra/receivercasts.t

@@ -0,0 +1,22 @@
+
+struct A { a : int }
+
+terra A.methods.foo(a : int)
+	return a + 1
+end
+
+function A.metamethods.__cast(from,to,exp)
+	if from == A and to == int then
+		return `exp.a
+	end
+	error("what")
+end
+
+
+
+terra testit()
+	var a = A { 5 }
+	return a:foo()
+end
+
+assert(6 == testit())