samples: add Terra samples

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

samples/Terra/evenodd.t

@@ -0,0 +1,20 @@
+terra iseven(a : uint) : bool
+	if a == 0 then
+		return true
+	else
+		return isodd(a - 1)
+	end
+end and
+terra isodd(a : uint) : bool
+	if a == 0 then
+		return false
+	else
+		return iseven(a - 1)
+	end
+end
+
+local test = require("test")
+test.eq(iseven(3),false)
+test.eq(iseven(2),true)
+test.eq(isodd(3),true)
+test.eq(isodd(2),false)